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- Sep 12, 2022
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Manfred Spraul authored
sysvipc_find_ipc() can be simplified further: - It uses a for() loop to locate the next entry in the idr. This can be replaced with idr_get_next(). - It receives two parameters (pos - which is actually an idr index and not a position, and new_pos, which is really a position). One parameter is sufficient. Link: https://lore.kernel.org/all/20210903052020.3265-3-manfred@colorfullife.com/ Link: https://lkml.kernel.org/r/20220805115733.104763-1-manfred@colorfullife.com Signed-off-by:
Manfred Spraul <manfred@colorfullife.com> Acked-by:
Davidlohr Bueso <dave@stgolabs.net> Acked-by:
Waiman Long <longman@redhat.com> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: <1vier1@web.de> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org>
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- Jan 22, 2022
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Muchun Song authored
Remove PDE_DATA() completely and replace it with pde_data(). [akpm@linux-foundation.org: fix naming clash in drivers/nubus/proc.c] [akpm@linux-foundation.org: now fix it properly] Link: https://lkml.kernel.org/r/20211124081956.87711-2-songmuchun@bytedance.com Signed-off-by:
Muchun Song <songmuchun@bytedance.com> Acked-by:
Christian Brauner <christian.brauner@ubuntu.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Alexey Gladkov <gladkov.alexey@gmail.com> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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- Nov 20, 2021
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Alexander Mikhalitsyn authored
Patch series "shm: shm_rmid_forced feature fixes". Some time ago I met kernel crash after CRIU restore procedure, fortunately, it was CRIU restore, so, I had dump files and could do restore many times and crash reproduced easily. After some investigation I've constructed the minimal reproducer. It was found that it's use-after-free and it happens only if sysctl kernel.shm_rmid_forced = 1. The key of the problem is that the exit_shm() function not handles shp's object destroy when task->sysvshm.shm_clist contains items from different IPC namespaces. In most cases this list will contain only items from one IPC namespace. How can this list contain object from different namespaces? The exit_shm() function is designed to clean up this list always when process leaves IPC namespace. But we made a mistake a long time ago and did not add a exit_shm() call into the setns() syscall procedures. The first idea was just to add this call to setns() syscall but it obviously changes semantics of setns() syscall and that's userspace-visible change. So, I gave up on this idea. The first real attempt to address the issue was just to omit forced destroy if we meet shp object not from current task IPC namespace [1]. But that was not the best idea because task->sysvshm.shm_clist was protected by rwsem which belongs to current task IPC namespace. It means that list corruption may occur. Second approach is just extend exit_shm() to properly handle shp's from different IPC namespaces [2]. This is really non-trivial thing, I've put a lot of effort into that but not believed that it's possible to make it fully safe, clean and clear. Thanks to the efforts of Manfred Spraul working an elegant solution was designed. Thanks a lot, Manfred! Eric also suggested the way to address the issue in ("[RFC][PATCH] shm: In shm_exit destroy all created and never attached segments") Eric's idea was to maintain a list of shm_clists one per IPC namespace, use lock-less lists. But there is some extra memory consumption-related concerns. An alternative solution which was suggested by me was implemented in ("shm: reset shm_clist on setns but omit forced shm destroy"). The idea is pretty simple, we add exit_shm() syscall to setns() but DO NOT destroy shm segments even if sysctl kernel.shm_rmid_forced = 1, we just clean up the task->sysvshm.shm_clist list. This chages semantics of setns() syscall a little bit but in comparision to the "naive" solution when we just add exit_shm() without any special exclusions this looks like a safer option. [1] https://lkml.org/lkml/2021/7/6/1108 [2] https://lkml.org/lkml/2021/7/14/736 This patch (of 2): Let's produce a warning if we trying to remove non-existing IPC object from IPC namespace kht/idr structures. This allows us to catch possible bugs when the ipc_rmid() function was called with inconsistent struct ipc_ids*, struct kern_ipc_perm* arguments. Link: https://lkml.kernel.org/r/20211027224348.611025-1-alexander.mikhalitsyn@virtuozzo.com Link: https://lkml.kernel.org/r/20211027224348.611025-2-alexander.mikhalitsyn@virtuozzo.com Co-developed-by:Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Andrei Vagin <avagin@gmail.com> Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Cc: Vasily Averin <vvs@virtuozzo.com> Cc: <stable@vger.kernel.org> Signed-off-by:
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- Sep 08, 2021
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Rafael Aquini authored
sysvipc_find_ipc() was left with a costly way to check if the offset position fed to it is bigger than the total number of IPC IDs in use. So much so that the time it takes to iterate over /proc/sysvipc/* files grows exponentially for a custom benchmark that creates "N" SYSV shm segments and then times the read of /proc/sysvipc/shm (milliseconds): 12 msecs to read 1024 segs from /proc/sysvipc/shm 18 msecs to read 2048 segs from /proc/sysvipc/shm 65 msecs to read 4096 segs from /proc/sysvipc/shm 325 msecs to read 8192 segs from /proc/sysvipc/shm 1303 msecs to read 16384 segs from /proc/sysvipc/shm 5182 msecs to read 32768 segs from /proc/sysvipc/shm The root problem lies with the loop that computes the total amount of ids in use to check if the "pos" feeded to sysvipc_find_ipc() grew bigger than "ids->in_use". That is a quite inneficient way to get to the maximum index in the id lookup table, specially when that value is already provided by struct ipc_ids.max_idx. This patch follows up on the optimization introduced via commit 15df03c8 ("sysvipc: make get_maxid O(1) again") and gets rid of the aforementioned costly loop replacing it by a simpler checkpoint based on ipc_get_maxidx() returned value, which allows for a smooth linear increase in time complexity for the same custom benchmark: 2 msecs to read 1024 segs from /proc/sysvipc/shm 2 msecs to read 2048 segs from /proc/sysvipc/shm 4 msecs to read 4096 segs from /proc/sysvipc/shm 9 msecs to read 8192 segs from /proc/sysvipc/shm 19 msecs to read 16384 segs from /proc/sysvipc/shm 39 msecs to read 32768 segs from /proc/sysvipc/shm Link: https://lkml.kernel.org/r/20210809203554.1562989-1-aquini@redhat.com Signed-off-by:Rafael Aquini <aquini@redhat.com> Acked-by:
Davidlohr Bueso <dbueso@suse.de> Acked-by:
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- Jul 01, 2021
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Manfred Spraul authored
If semctl(), msgctl() and shmctl() are called with IPC_INFO, SEM_INFO, MSG_INFO or SHM_INFO, then the return value is the index of the highest used index in the kernel's internal array recording information about all SysV objects of the requested type for the current namespace. (This information can be used with repeated ..._STAT or ..._STAT_ANY operations to obtain information about all SysV objects on the system.) There is a cache for this value. But when the cache needs up be updated, then the highest used index is determined by looping over all possible values. With the introduction of IPCMNI_EXTEND_SHIFT, this could be a loop over 16 million entries. And due to /proc/sys/kernel/*next_id, the index values do not need to be consecutive. With <write 16000000 to msg_next_id>, msgget(), msgctl(,IPC_RMID) in a loop, I have observed a performance increase of around factor 13000. As there is no get_last() function for idr structures: Implement a "get_last()" using a binary search. As far as I see, ipc is the only user that needs get_last(), thus implement it in ipc/util.c and not in a central location. [akpm@linux-foundation.org: tweak comment, fix typo] Link: https://lkml.kernel.org/r/20210425075208.11777-2-manfred@colorfullife.com Signed-off-by:
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- May 14, 2020
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Vasily Averin authored
Commit 89163f93 ("ipc/util.c: sysvipc_find_ipc() should increase position index") is causing this bug (seen on 5.6.8): # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages # ipcmk -Q Message queue id: 0 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x82db8127 0 root 644 0 0 # ipcmk -Q Message queue id: 1 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x82db8127 0 root 644 0 0 0x76d1fb2a 1 root 644 0 0 # ipcrm -q 0 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x76d1fb2a 1 root 644 0 0 0x76d1fb2a 1 root 644 0 0 # ipcmk -Q Message queue id: 2 # ipcrm -q 2 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x76d1fb2a 1 root 644 0 0 0x76d1fb2a 1 root 644 0 0 # ipcmk -Q Message queue id: 3 # ipcrm -q 1 # ipcs -q ------ Message Queues -------- key msqid owner perms used-bytes messages 0x7c982867 3 root 644 0 0 0x7c982867 3 root 644 0 0 0x7c982867 3 root 644 0 0 0x7c982867 3 root 644 0 0 Whenever an IPC item with a low id is deleted, the items with higher ids are duplicated, as if filling a hole. new_pos should jump through hole of unused ids, pos can be updated inside "for" cycle. Fixes: 89163f93 ("ipc/util.c: sysvipc_find_ipc() should increase position index") Reported-by:
Andreas Schwab <schwab@suse.de> Reported-by:
Randy Dunlap <rdunlap@infradead.org> Signed-off-by:
Vasily Averin <vvs@virtuozzo.com> Signed-off-by:
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- Apr 11, 2020
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Vasily Averin authored
If seq_file .next function does not change position index, read after some lseek can generate unexpected output. https://bugzilla.kernel.org/show_bug.cgi?id=206283 Signed-off-by:
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- Apr 07, 2020
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Alexey Dobriyan authored
Now that "struct proc_ops" exist we can start putting there stuff which could not fly with VFS "struct file_operations"... Most of fs/proc/inode.c file is dedicated to make open/read/.../close reliable in the event of disappearing /proc entries which usually happens if module is getting removed. Files like /proc/cpuinfo which never disappear simply do not need such protection. Save 2 atomic ops, 1 allocation, 1 free per open/read/close sequence for such "permanent" files. Enable "permanent" flag for /proc/cpuinfo /proc/kmsg /proc/modules /proc/slabinfo /proc/stat /proc/sysvipc/* /proc/swaps More will come once I figure out foolproof way to prevent out module authors from marking their stuff "permanent" for performance reasons when it is not. This should help with scalability: benchmark is "read /proc/cpuinfo R times by N threads scattered over the system". N R t, s (before) t, s (after) ----------------------------------------------------- 64 4096 1.582458 1.530502 -3.2% 256 4096 6.371926 6.125168 -3.9% 1024 4096 25.64888 24.47528 -4.6% Benchmark source: #include <chrono> #include <iostream> #include <thread> #include <vector> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> const int NR_CPUS = sysconf(_SC_NPROCESSORS_ONLN); int N; const char *filename; int R; int xxx = 0; int glue(int n) { cpu_set_t m; CPU_ZERO(&m); CPU_SET(n, &m); return sched_setaffinity(0, sizeof(cpu_set_t), &m); } void f(int n) { glue(n % NR_CPUS); while (*(volatile int *)&xxx == 0) { } for (int i = 0; i < R; i++) { int fd = open(filename, O_RDONLY); char buf[4096]; ssize_t rv = read(fd, buf, sizeof(buf)); asm volatile ("" :: "g" (rv)); close(fd); } } int main(int argc, char *argv[]) { if (argc < 4) { std::cerr << "usage: " << argv[0] << ' ' << "N /proc/filename R "; return 1; } N = atoi(argv[1]); filename = argv[2]; R = atoi(argv[3]); for (int i = 0; i < NR_CPUS; i++) { if (glue(i) == 0) break; } std::vector<std::thread> T; T.reserve(N); for (int i = 0; i < N; i++) { T.emplace_back(f, i); } auto t0 = std::chrono::system_clock::now(); { *(volatile int *)&xxx = 1; for (auto& t: T) { t.join(); } } auto t1 = std::chrono::system_clock::now(); std::chrono::duration<double> dt = t1 - t0; std::cout << dt.count() << ' '; return 0; } P.S.: Explicit randomization marker is added because adding non-function pointer will silently disable structure layout randomization. [akpm@linux-foundation.org: coding style fixes] Reported-by:kbuild test robot <lkp@intel.com> Reported-by:
Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by:
Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by:
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- Feb 04, 2020
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Alexey Dobriyan authored
The most notable change is DEFINE_SHOW_ATTRIBUTE macro split in seq_file.h. Conversion rule is: llseek => proc_lseek unlocked_ioctl => proc_ioctl xxx => proc_xxx delete ".owner = THIS_MODULE" line [akpm@linux-foundation.org: fix drivers/isdn/capi/kcapi_proc.c] [sfr@canb.auug.org.au: fix kernel/sched/psi.c] Link: http://lkml.kernel.org/r/20200122180545.36222f50@canb.auug.org.au Link: http://lkml.kernel.org/r/20191225172546.GB13378@avx2 Signed-off-by:
Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by:
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- Dec 09, 2019
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Pankaj Bharadiya authored
Replace all the occurrences of FIELD_SIZEOF() with sizeof_field() except at places where these are defined. Later patches will remove the unused definition of FIELD_SIZEOF(). This patch is generated using following script: EXCLUDE_FILES="include/linux/stddef.h|include/linux/kernel.h" git grep -l -e "\bFIELD_SIZEOF\b" | while read file; do if [[ "$file" =~ $EXCLUDE_FILES ]]; then continue fi sed -i -e 's/\bFIELD_SIZEOF\b/sizeof_field/g' $file; done Signed-off-by:
Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com> Link: https://lore.kernel.org/r/20190924105839.110713-3-pankaj.laxminarayan.bharadiya@intel.com Co-developed-by:
Kees Cook <keescook@chromium.org> Signed-off-by:
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- May 15, 2019
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Manfred Spraul authored
For ipcmni_extend mode, the sequence number space is only 7 bits. So the chance of id reuse is relatively high compared with the non-extended mode. To alleviate this id reuse problem, this patch enables cyclic allocation for the index to the radix tree (idx). The disadvantage is that this can cause a slight slow-down of the fast path, as the radix tree could be higher than necessary. To limit the radix tree height, I have chosen the following limits: 1) The cycling is done over in_use*1.5. 2) At least, the cycling is done over "normal" ipcnmi mode: RADIX_TREE_MAP_SIZE elements "ipcmni_extended": 4096 elements Result: - for normal mode: No change for <= 42 active ipc elements. With more than 42 active ipc elements, a 2nd level would be added to the radix tree. Without cyclic allocation, a 2nd level would be added only with more than 63 active elements. - for extended mode: Cycling creates always at least a 2-level radix tree. With more than 2730 active objects, a 3rd level would be added, instead of > 4095 active objects until the 3rd level is added without cyclic allocation. For a 2-level radix tree compared to a 1-level radix tree, I have observed < 1% performance impact. Notes: 1) Normal "x=semget();y=semget();" is unaffected: Then the idx is e.g. a and a+1, regardless if idr_alloc() or idr_alloc_cyclic() is used. 2) The -1% happens in a microbenchmark after this situation: x=semget(); for(i=0;i<4000;i++) {t=semget();semctl(t,0,IPC_RMID);} y=semget(); Now perform semget calls on x and y that do not sleep. 3) The worst-case reuse cycle time is unfortunately unaffected: If you have 2^24-1 ipc objects allocated, and get/remove the last possible element in a loop, then the id is reused after 128 get/remove pairs. Performance check: A microbenchmark that performes no-op semop() randomly on two IDs, with only these two IDs allocated. The IDs were set using /proc/sys/kernel/sem_next_id. The test was run 5 times, averages are shown. 1 & 2: Base (6.22 seconds for 10.000.000 semops) 1 & 40: -0.2% 1 & 3348: - 0.8% 1 & 27348: - 1.6% 1 & 15777204: - 3.2% Or: ~12.6 cpu cycles per additional radix tree level. The cpu is an Intel I3-5010U. ~1300 cpu cycles/syscall is slower than what I remember (spectre impact?). V2 of the patch: - use "min" and "max" - use RADIX_TREE_MAP_SIZE * RADIX_TREE_MAP_SIZE instead of (2<<12). [akpm@linux-foundation.org: fix max() warning] Link: http://lkml.kernel.org/r/20190329204930.21620-3-longman@redhat.com Signed-off-by: -
Manfred Spraul authored
Rewrite, based on the patch from Waiman Long: The mixing in of a sequence number into the IPC IDs is probably to avoid ID reuse in userspace as much as possible. With ipcmni_extend mode, the number of usable sequence numbers is greatly reduced leading to higher chance of ID reuse. To address this issue, we need to conserve the sequence number space as much as possible. Right now, the sequence number is incremented for every new ID created. In reality, we only need to increment the sequence number when new allocated ID is not greater than the last one allocated. It is in such case that the new ID may collide with an existing one. This is being done irrespective of the ipcmni mode. In order to avoid any races, the index is first allocated and then the pointer is replaced. Changes compared to the initial patch: - Handle failures from idr_alloc(). - Avoid that concurrent operations can see the wrong sequence number. (This is achieved by using idr_replace()). - IPCMNI_SEQ_SHIFT is not a constant, thus renamed to ipcmni_seq_shift(). - IPCMNI_SEQ_MAX is not a constant, thus renamed to ipcmni_seq_max(). Link: http://lkml.kernel.org/r/20190329204930.21620-2-longman@redhat.com Signed-off-by:
Matthew Wilcox <willy@infradead.org> Acked-by:
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Waiman Long authored
The maximum number of unique System V IPC identifiers was limited to 32k. That limit should be big enough for most use cases. However, there are some users out there requesting for more, especially those that are migrating from Solaris which uses 24 bits for unique identifiers. To satisfy the need of those users, a new boot time kernel option "ipcmni_extend" is added to extend the IPCMNI value to 16M. This is a 512X increase which should be big enough for users out there that need a large number of unique IPC identifier. The use of this new option will change the pattern of the IPC identifiers returned by functions like shmget(2). An application that depends on such pattern may not work properly. So it should only be used if the users really need more than 32k of unique IPC numbers. This new option does have the side effect of reducing the maximum number of unique sequence numbers from 64k down to 128. So it is a trade-off. The computation of a new IPC id is not done in the performance critical path. So a little bit of additional overhead shouldn't have any real performance impact. Link: http://lkml.kernel.org/r/20190329204930.21620-1-longman@redhat.com Signed-off-by:
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- Apr 08, 2019
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NeilBrown authored
This patch changes rhashtables to use a bit_spin_lock on BIT(1) of the bucket pointer to lock the hash chain for that bucket. The benefits of a bit spin_lock are: - no need to allocate a separate array of locks. - no need to have a configuration option to guide the choice of the size of this array - locking cost is often a single test-and-set in a cache line that will have to be loaded anyway. When inserting at, or removing from, the head of the chain, the unlock is free - writing the new address in the bucket head implicitly clears the lock bit. For __rhashtable_insert_fast() we ensure this always happens when adding a new key. - even when lockings costs 2 updates (lock and unlock), they are in a cacheline that needs to be read anyway. The cost of using a bit spin_lock is a little bit of code complexity, which I think is quite manageable. Bit spin_locks are sometimes inappropriate because they are not fair - if multiple CPUs repeatedly contend of the same lock, one CPU can easily be starved. This is not a credible situation with rhashtable. Multiple CPUs may want to repeatedly add or remove objects, but they will typically do so at different buckets, so they will attempt to acquire different locks. As we have more bit-locks than we previously had spinlocks (by at least a factor of two) we can expect slightly less contention to go with the slightly better cache behavior and reduced memory consumption. To enhance type checking, a new struct is introduced to represent the pointer plus lock-bit that is stored in the bucket-table. This is "struct rhash_lock_head" and is empty. A pointer to this needs to be cast to either an unsigned lock, or a "struct rhash_head *" to be useful. Variables of this type are most often called "bkt". Previously "pprev" would sometimes point to a bucket, and sometimes a ->next pointer in an rhash_head. As these are now different types, pprev is NULL when it would have pointed to the bucket. In that case, 'blk' is used, together with correct locking protocol. Signed-off-by:
NeilBrown <neilb@suse.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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- Aug 22, 2018
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Manfred Spraul authored
ipc_getref has still a return value of type "int", matching the atomic_t interface of atomic_inc_not_zero()/atomic_add_unless(). ipc_getref now uses refcount_inc_not_zero, which has a return value of type "bool". Therefore, update the return code to avoid implicit conversions. Link: http://lkml.kernel.org/r/20180712185241.4017-13-manfred@colorfullife.com Signed-off-by:
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Manfred Spraul authored
The varable names got a mess, thus standardize them again: id: user space id. Called semid, shmid, msgid if the type is known. Most functions use "id" already. idx: "index" for the idr lookup Right now, some functions use lid, ipc_addid() already uses idx as the variable name. seq: sequence number, to avoid quick collisions of the user space id key: user space key, used for the rhash tree Link: http://lkml.kernel.org/r/20180712185241.4017-12-manfred@colorfullife.com Signed-off-by: -
Davidlohr Bueso authored
Now that we know that rhashtable_init() will not fail, we can get rid of a lot of the unnecessary cleanup paths when the call errored out. [manfred@colorfullife.com: variable name added to util.h to resolve checkpatch warning] Link: http://lkml.kernel.org/r/20180712185241.4017-11-manfred@colorfullife.com Signed-off-by:
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Davidlohr Bueso authored
In sysvipc we have an ids->tables_initialized regarding the rhashtable, introduced in 0cfb6aee ("ipc: optimize semget/shmget/msgget for lots of keys") It's there, specifically, to prevent nil pointer dereferences, from using an uninitialized api. Considering how rhashtable_init() can fail (probably due to ENOMEM, if anything), this made the overall ipc initialization capable of failure as well. That alone is ugly, but fine, however I've spotted a few issues regarding the semantics of tables_initialized (however unlikely they may be): - There is inconsistency in what we return to userspace: ipc_addid() returns ENOSPC which is certainly _wrong_, while ipc_obtain_object_idr() returns EINVAL. - After we started using rhashtables, ipc_findkey() can return nil upon !tables_initialized, but the caller expects nil for when the ipc structure isn't found, and can therefore call into ipcget() callbacks. Now that rhashtable initialization cannot fail, we can properly get rid of the hack altogether. [manfred@colorfullife.com: commit id extended to 12 digits] Link: http://lkml.kernel.org/r/20180712185241.4017-10-manfred@colorfullife.com Signed-off-by:
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Davidlohr Bueso authored
ipc/util.c contains multiple functions to get the ipc object pointer given an id number. There are two sets of function: One set verifies the sequence counter part of the id number, other functions do not check the sequence counter. The standard for function names in ipc/util.c is - ..._check() functions verify the sequence counter - ..._idr() functions do not verify the sequence counter ipc_lock() is an exception: It does not verify the sequence counter value, but this is not obvious from the function name. Furthermore, shm.c is the only user of this helper. Thus, we can simply move the logic into shm_lock() and get rid of the function altogether. [manfred@colorfullife.com: most of changelog] Link: http://lkml.kernel.org/r/20180712185241.4017-7-manfred@colorfullife.com Signed-off-by:
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Manfred Spraul authored
The comment that explains ipc_obtain_object_check is wrong: The function checks the sequence number, not the reference counter. Note that checking the reference counter would be meaningless: The reference counter is decreased without holding any locks, thus an object with kern_ipc_perm.deleted=true may disappear at the end of the next rcu grace period. Link: http://lkml.kernel.org/r/20180712185241.4017-6-manfred@colorfullife.com Signed-off-by:
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Manfred Spraul authored
Both the comment and the name of ipcctl_pre_down_nolock() are misleading: The function must be called while holdling the rw semaphore. Therefore the patch renames the function to ipcctl_obtain_check(): This name matches the other names used in util.c: - "obtain" function look up a pointer in the idr, without acquiring the object lock. - The caller is responsible for locking. - _check means that the sequence number is checked. Link: http://lkml.kernel.org/r/20180712185241.4017-5-manfred@colorfullife.com Signed-off-by:
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Manfred Spraul authored
ipc_addid() is impossible to use: - for certain failures, the caller must not use ipc_rcu_putref(), because the reference counter is not yet initialized. - for other failures, the caller must use ipc_rcu_putref(), because parallel operations could be ongoing already. The patch cleans that up, by initializing the refcount early, and by modifying all callers. The issues is related to the finding of syzbot+2827ef6b3385deb07eaf@syzkaller.appspotmail.com: syzbot found an issue with reading kern_ipc_perm.seq, here both read and write to already released memory could happen. Link: http://lkml.kernel.org/r/20180712185241.4017-4-manfred@colorfullife.com Signed-off-by:
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Manfred Spraul authored
ipc_addid() initializes kern_ipc_perm.seq after having called idr_alloc() (within ipc_idr_alloc()). Thus a parallel semop() or msgrcv() that uses ipc_obtain_object_check() may see an uninitialized value. The patch moves the initialization of kern_ipc_perm.seq before the calls of idr_alloc(). Notes: 1) This patch has a user space visible side effect: If /proc/sys/kernel/*_next_id is used (i.e.: checkpoint/restore) and if semget()/msgget()/shmget() fails in the final step of adding the id to the rhash tree, then .._next_id is cleared. Before the patch, is remained unmodified. There is no change of the behavior after a successful ..get() call: It always clears .._next_id, there is no impact to non checkpoint/restore code as that code does not use .._next_id. 2) The patch correctly documents that after a call to ipc_idr_alloc(), the full tear-down sequence must be used. The callers of ipc_addid() do not fullfill that, i.e. more bugfixes are required. The patch is a squash of a patch from Dmitry and my own changes. Link: http://lkml.kernel.org/r/20180712185241.4017-3-manfred@colorfullife.com Reported-by:
<syzbot+2827ef6b3385deb07eaf@syzkaller.appspotmail.com> Signed-off-by:
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- Jun 22, 2018
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NeilBrown authored
Due to the use of rhashtables in net namespaces, rhashtable.h is included in lots of the kernel, so a small changes can required a large recompilation. This makes development painful. This patch splits out rhashtable-types.h which just includes the major type declarations, and does not include (non-trivial) inline code. rhashtable.h is no longer included by anything in the include/ directory. Common include files only include rhashtable-types.h so a large recompilation is only triggered when that changes. Acked-by:
Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by:
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- Apr 11, 2018
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Alexey Dobriyan authored
Move the proc_mkdir() call within the sysvipc subsystem such that we avoid polluting proc_root_init() with petty cpp. [dave@stgolabs.net: contributed changelog] Link: http://lkml.kernel.org/r/20180216161732.GA10297@avx2 Signed-off-by:
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- Mar 24, 2018
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Eric W. Biederman authored
Capture the pid namespace when /proc/sysvipc/msg /proc/sysvipc/shm and /proc/sysvipc/sem are opened, and make it available through the new helper ipc_seq_pid_ns. This makes it possible to report the pids in these files in the pid namespace of the opener of the files. Implement ipc_update_pid. A simple impline helper that will only update a struct pid pointer if the new value does not equal the old value. This removes the need for wordy code sequences like: old = object->pid; object->pid = new; put_pid(old); and old = object->pid; if (old != new) { object->pid = new; put_pid(old); } Allowing the following to be written instead: ipc_update_pid(&object->pid, new); Which is easier to read and ensures that the pid reference count is not touched the old and the new values are the same. Not touching the reference count in this case is important to help avoid issues like af_unix experienced, where multiple threads of the same process managed to bounce the struct pid between cpu cache lines, but updating the pids reference count. Signed-off-by:"Eric W. Biederman" <ebiederm@xmission.com>
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- Feb 07, 2018
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Philippe Mikoyan authored
As described in the title, this patch fixes <ipc>id_ds inconsistency when <ipc>ctl_stat executes concurrently with some ds-changing function, e.g. shmat, msgsnd or whatever. For instance, if shmctl(IPC_STAT) is running concurrently with shmat, following data structure can be returned: {... shm_lpid = 0, shm_nattch = 1, ...} Link: http://lkml.kernel.org/r/20171202153456.6514-1-philippe.mikoyan@skat.systems Signed-off-by:Philippe Mikoyan <philippe.mikoyan@skat.systems> Reviewed-by:
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- Nov 18, 2017
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Davidlohr Bueso authored
For a custom microbenchmark on a 3.30GHz Xeon SandyBridge, which calls IPC_STAT over and over, it was calculated that, on avg the cost of ipc_get_maxid() for increasing amounts of keys was: 10 keys: ~900 cycles 100 keys: ~15000 cycles 1000 keys: ~150000 cycles 10000 keys: ~2100000 cycles This is unsurprising as maxid is currently O(n). By having the max_id available in O(1) we save all those cycles for each semctl(_STAT) command, the idr_find can be expensive -- which some real (customer) workloads actually poll on. Note that this used to be the case, until commit 7ca7e564 ("ipc: store ipcs into IDRs"). The cost is the extra idr_find when doing RMIDs, but we simply go backwards, and should not take too many iterations to find the new value. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20170831172049.14576-5-dave@stgolabs.net Signed-off-by:
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Davidlohr Bueso authored
This is better understood as a limit, instead of size; exactly like the function comment indicates. Rename it. Link: http://lkml.kernel.org/r/20170831172049.14576-4-dave@stgolabs.net Signed-off-by:
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Davidlohr Bueso authored
Patch series "sysvipc: ipc-key management improvements". Here are a few improvements I spotted while eyeballing Guillaume's rhashtable implementation for ipc keys. The first and fourth patches are the interesting ones, the middle two are trivial. This patch (of 4): The next_id object-allocation functionality was introduced in commit 03f59566 ("ipc: add sysctl to specify desired next object id"). Given that these new entries are _only_ exported under the CONFIG_CHECKPOINT_RESTORE option, there is no point for the common case to even know about ->next_id. As such rewrite ipc_buildid() such that it can do away with the field as well as unnecessary branches when adding a new identifier. The end result also better differentiates both cases, so the code ends up being cleaner; albeit the small duplications regarding the default case. [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/20170831172049.14576-2-dave@stgolabs.net Signed-off-by:
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- Nov 02, 2017
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Greg Kroah-Hartman authored
Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by:
Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by:
Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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- Sep 09, 2017
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Guillaume Knispel authored
ipc_findkey() used to scan all objects to look for the wanted key. This is slow when using a high number of keys. This change adds an rhashtable of kern_ipc_perm objects in ipc_ids, so that one lookup cease to be O(n). This change gives a 865% improvement of benchmark reaim.jobs_per_min on a 56 threads Intel(R) Xeon(R) CPU E5-2695 v3 @ 2.30GHz with 256G memory [1] Other (more micro) benchmark results, by the author: On an i5 laptop, the following loop executed right after a reboot took, without and with this change: for (int i = 0, k=0x424242; i < KEYS; ++i) semget(k++, 1, IPC_CREAT | 0600); total total max single max single KEYS without with call without call with 1 3.5 4.9 µs 3.5 4.9 10 7.6 8.6 µs 3.7 4.7 32 16.2 15.9 µs 4.3 5.3 100 72.9 41.8 µs 3.7 4.7 1000 5,630.0 502.0 µs * * 10000 1,340,000.0 7,240.0 µs * * 31900 17,600,000.0 22,200.0 µs * * *: unreliable measure: high variance The duration for a lookup-only usage was obtained by the same loop once the keys are present: total total max single max single KEYS without with call without call with 1 2.1 2.5 µs 2.1 2.5 10 4.5 4.8 µs 2.2 2.3 32 13.0 10.8 µs 2.3 2.8 100 82.9 25.1 µs * 2.3 1000 5,780.0 217.0 µs * * 10000 1,470,000.0 2,520.0 µs * * 31900 17,400,000.0 7,810.0 µs * * Finally, executing each semget() in a new process gave, when still summing only the durations of these syscalls: creation: total total KEYS without with 1 3.7 5.0 µs 10 32.9 36.7 µs 32 125.0 109.0 µs 100 523.0 353.0 µs 1000 20,300.0 3,280.0 µs 10000 2,470,000.0 46,700.0 µs 31900 27,800,000.0 219,000.0 µs lookup-only: total total KEYS without with 1 2.5 2.7 µs 10 25.4 24.4 µs 32 106.0 72.6 µs 100 591.0 352.0 µs 1000 22,400.0 2,250.0 µs 10000 2,510,000.0 25,700.0 µs 31900 28,200,000.0 115,000.0 µs [1] http://lkml.kernel.org/r/20170814060507.GE23258@yexl-desktop Link: http://lkml.kernel.org/r/20170815194954.ck32ta2z35yuzpwp@debix Signed-off-by:Guillaume Knispel <guillaume.knispel@supersonicimagine.com> Reviewed-by:
Marc Pardo <marc.pardo@supersonicimagine.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Kees Cook <keescook@chromium.org> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Serge Hallyn <serge@hallyn.com> Cc: Andrey Vagin <avagin@openvz.org> Cc: Guillaume Knispel <guillaume.knispel@supersonicimagine.com> Cc: Marc Pardo <marc.pardo@supersonicimagine.com> Signed-off-by:
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Elena Reshetova authored
refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations. Link: http://lkml.kernel.org/r/1499417992-3238-4-git-send-email-elena.reshetova@intel.com Signed-off-by:
Elena Reshetova <elena.reshetova@intel.com> Signed-off-by:
Hans Liljestrand <ishkamiel@gmail.com> Signed-off-by:
David Windsor <dwindsor@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: <arozansk@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Manfred Spraul <manfred@colorfullife.com> Signed-off-by:
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- Jul 13, 2017
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Kees Cook authored
Only after ipc_addid() has succeeded will refcounting be used, so move initialization into ipc_addid() and remove from open-coded *_alloc() routines. Link: http://lkml.kernel.org/r/20170525185107.12869-17-manfred@colorfullife.com Signed-off-by:
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Kees Cook authored
No callers remain for ipc_rcu_alloc(). Drop the function. [manfred@colorfullife.com: Rediff because the memset was temporarily inside ipc_rcu_free()] Link: http://lkml.kernel.org/r/20170525185107.12869-13-manfred@colorfullife.com Signed-off-by:
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Kees Cook authored
There are no more callers of ipc_rcu_free(), so remove it. Link: http://lkml.kernel.org/r/20170525185107.12869-9-manfred@colorfullife.com Signed-off-by:
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Kees Cook authored
The only users of ipc_alloc() were ipc_rcu_alloc() and the on-heap sem_io fall-back memory. Better to just open-code these to make things easier to read. [manfred@colorfullife.com: Rediff due to inclusion of memset() into ipc_rcu_alloc()] Link: http://lkml.kernel.org/r/20170525185107.12869-5-manfred@colorfullife.com Signed-off-by:
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Manfred Spraul authored
ipc has two management structures that exist for every id: - struct kern_ipc_perm, it contains e.g. the permissions. - struct ipc_rcu, it contains the rcu head for rcu handling and the refcount. The patch merges both structures. As a bonus, we may save one cacheline, because both structures are cacheline aligned. In addition, it reduces the number of casts, instead most codepaths can use container_of. To simplify code, the ipc_rcu_alloc initializes the allocation to 0. [manfred@colorfullife.com: really include the memset() into ipc_alloc_rcu()] Link: http://lkml.kernel.org/r/564f8612-0601-b267-514f-a9f650ec9b32@colorfullife.com Link: http://lkml.kernel.org/r/20170525185107.12869-3-manfred@colorfullife.com Signed-off-by:
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- May 09, 2017
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Michal Hocko authored
Patch series "kvmalloc", v5. There are many open coded kmalloc with vmalloc fallback instances in the tree. Most of them are not careful enough or simply do not care about the underlying semantic of the kmalloc/page allocator which means that a) some vmalloc fallbacks are basically unreachable because the kmalloc part will keep retrying until it succeeds b) the page allocator can invoke a really disruptive steps like the OOM killer to move forward which doesn't sound appropriate when we consider that the vmalloc fallback is available. As it can be seen implementing kvmalloc requires quite an intimate knowledge if the page allocator and the memory reclaim internals which strongly suggests that a helper should be implemented in the memory subsystem proper. Most callers, I could find, have been converted to use the helper instead. This is patch 6. There are some more relying on __GFP_REPEAT in the networking stack which I have converted as well and Eric Dumazet was not opposed [2] to convert them as well. [1] http://lkml.kernel.org/r/20170130094940.13546-1-mhocko@kernel.org [2] http://lkml.kernel.org/r/1485273626.16328.301.camel@edumazet-glaptop3.roam.corp.google.com This patch (of 9): Using kmalloc with the vmalloc fallback for larger allocations is a common pattern in the kernel code. Yet we do not have any common helper for that and so users have invented their own helpers. Some of them are really creative when doing so. Let's just add kv[mz]alloc and make sure it is implemented properly. This implementation makes sure to not make a large memory pressure for > PAGE_SZE requests (__GFP_NORETRY) and also to not warn about allocation failures. This also rules out the OOM killer as the vmalloc is a more approapriate fallback than a disruptive user visible action. This patch also changes some existing users and removes helpers which are specific for them. In some cases this is not possible (e.g. ext4_kvmalloc, libcfs_kvzalloc) because those seems to be broken and require GFP_NO{FS,IO} context which is not vmalloc compatible in general (note that the page table allocation is GFP_KERNEL). Those need to be fixed separately. While we are at it, document that __vmalloc{_node} about unsupported gfp mask because there seems to be a lot of confusion out there. kvmalloc_node will warn about GFP_KERNEL incompatible (which are not superset) flags to catch new abusers. Existing ones would have to die slowly. [sfr@canb.auug.org.au: f2fs fixup] Link: http://lkml.kernel.org/r/20170320163735.332e64b7@canb.auug.org.au Link: http://lkml.kernel.org/r/20170306103032.2540-2-mhocko@kernel.org Signed-off-by:
Michal Hocko <mhocko@suse.com> Signed-off-by:
Vlastimil Babka <vbabka@suse.cz> Cc: John Hubbard <jhubbard@nvidia.com> Cc: David Miller <davem@davemloft.net> Signed-off-by:
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- Apr 02, 2017
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Mauro Carvalho Chehab authored
./lib/string.c:134: WARNING: Inline emphasis start-string without end-string. ./mm/filemap.c:522: WARNING: Inline interpreted text or phrase reference start-string without end-string. ./mm/filemap.c:1283: ERROR: Unexpected indentation. ./mm/filemap.c:3003: WARNING: Inline interpreted text or phrase reference start-string without end-string. ./mm/vmalloc.c:1544: WARNING: Inline emphasis start-string without end-string. ./mm/page_alloc.c:4245: ERROR: Unexpected indentation. ./ipc/util.c:676: ERROR: Unexpected indentation. ./drivers/pci/irq.c:35: WARNING: Block quote ends without a blank line; unexpected unindent. ./security/security.c:109: ERROR: Unexpected indentation. ./security/security.c:110: WARNING: Definition list ends without a blank line; unexpected unindent. ./block/genhd.c:275: WARNING: Inline strong start-string without end-string. ./block/genhd.c:283: WARNING: Inline strong start-string without end-string. ./include/linux/clk.h:134: WARNING: Inline emphasis start-string without end-string. ./include/linux/clk.h:134: WARNING: Inline emphasis start-string without end-string. ./ipc/util.c:477: ERROR: Unknown target name: "s". Signed-off-by:
Mauro Carvalho Chehab <mchehab@s-opensource.com> Acked-by:
Bjorn Helgaas <bhelgaas@google.com> Signed-off-by:
Jonathan Corbet <corbet@lwn.net>
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