If the target ring is using IORING_SETUP_SINGLE_ISSUER and we're posting
a message from a different thread, then we need to ensure that the
fallback task_work that posts the CQE knwos about the flags passing as
well. If not we'll always be posting 0 as the flags.

Fixes: 3563d7ed58a5 ("io_uring/msg_ring: Pass custom flags to the cqe")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch adds a new flag (IORING_MSG_RING_FLAGS_PASS) in the message
ring operations (IORING_OP_MSG_RING). This new flag enables the sender
to specify custom flags, which will be copied over to cqe->flags in the
receiving ring.  These custom flags should be specified using the
sqe->file_index field.

This mechanism provides additional flexibility when sending messages
between rings.

Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20230103160507.617416-1-leitao@debian.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>

IORING_SETUP_R_DISABLED rings don't have the submitter task set, so
it's not always safe to use ->submitter_task. Disallow posting msg_ring
messaged to disabled rings. Also add task NULL check for loosy sync
around testing for IORING_SETUP_R_DISABLED.

Cc: stable@vger.kernel.org
Fixes: 6d043ee1 ("io_uring: do msg_ring in target task via tw")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

There is a couple of problems with queueing a tw in io_msg_ring_data()
for remote execution. First, once we queue it the target ring can
go away and so setting IORING_SQ_TASKRUN there is not safe. Secondly,
the userspace might not expect IORING_SQ_TASKRUN.

Extract a helper and uniformly use TWA_SIGNAL without TWA_SIGNAL_NO_IPI
tricks for now, just as it was done in the original patch.

Cc: stable@vger.kernel.org
Fixes: 6d043ee1 ("io_uring: do msg_ring in target task via tw")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

If the target ring is configured with IOPOLL, then we always need to hold
the target ring uring_lock before posting CQEs. We could just grab it
unconditionally, but since we don't expect many target rings to be of this
type, make grabbing the uring_lock conditional on the ring type.

Link: https://lore.kernel.org/io-uring/Y8krlYa52%2F0YGqkg@ip-172-31-85-199.ec2.internal/


Reported-by: Xingyuan Mo <hdthky0@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

In preparation for needing them somewhere else, move them and get rid of
the unused 'issue_flags' for the unlock side.

No functional changes in this patch.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Before the recent change, we didn't even wake the targeted task when
posting the cqe remotely. Now we do wake it, but we do want to ensure
that the recipient knows there's potential work there that needs to
get processed to get the CQE posted.

OR in IORING_SQ_TASKRUN for that purpose.

Link: https://lore.kernel.org/io-uring/2843c6b4-ba9a-b67d-e0f4-957f42098489@kernel.dk/


Fixes: 6d043ee1 ("io_uring: do msg_ring in target task via tw")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

While executing in a context of one io_uring instance msg_ring
manipulates another ring. We're trying to keep CQEs posting contained in
the context of the ring-owner task, use task_work to send the request to
the target ring's task when we're modifying its CQ or trying to install
a file. Note, we can't safely use io_uring task_work infra and have to
use task_work directly.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/4d76c7b28ed5d71b520de4482fbb7f660f21cd80.1670384893.git.asml.silence@gmail.com


[axboe: use TWA_SIGNAL_NO_IPI]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Extract a helper called io_msg_install_complete() from io_msg_send_fd(),
will be used later.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1500ca1054cc4286a3ee1c60aacead57fcdfa02a.1670384893.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

We don't need to take both uring_locks at once, msg_ring can be split in
two parts, first getting a file from the filetable of the first ring and
then installing it into the second one.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a80ecc2bc99c3b3f2cf20015d618b7c51419a797.1670384893.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

msg_ring will fail the request if it can't lock rings, instead punt it
to io-wq as was originally intended.

Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/4697f05afcc37df5c8f89e2fe6d9c7c19f0241f9.1670384893.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

We should not be messing with req->file outside of core paths. Clearing
it makes msg_ring non reentrant, i.e. luckily io_msg_send_fd() fails the
request on failed io_double_lock_ctx() but clearly was originally
intended to do retries instead.

Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e5ac9edadb574fe33f6d727cb8f14ce68262a684.1670384893.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

The only call sites which would not allow overflow are also call sites
which would use the io_aux_cqe as they care about ordering.

So remove this parameter from io_post_aux_cqe.

Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221124093559.3780686-9-dylany@meta.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Syzkaller produced the below call trace:

 BUG: KASAN: null-ptr-deref in io_msg_ring+0x3cb/0x9f0
 Write of size 8 at addr 0000000000000070 by task repro/16399

 CPU: 0 PID: 16399 Comm: repro Not tainted 6.1.0-rc1 #28
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7
 Call Trace:
  <TASK>
  dump_stack_lvl+0xcd/0x134
  ? io_msg_ring+0x3cb/0x9f0
  kasan_report+0xbc/0xf0
  ? io_msg_ring+0x3cb/0x9f0
  kasan_check_range+0x140/0x190
  io_msg_ring+0x3cb/0x9f0
  ? io_msg_ring_prep+0x300/0x300
  io_issue_sqe+0x698/0xca0
  io_submit_sqes+0x92f/0x1c30
  __do_sys_io_uring_enter+0xae4/0x24b0
....
 RIP: 0033:0x7f2eaf8f8289
 RSP: 002b:00007fff40939718 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2eaf8f8289
 RDX: 0000000000000000 RSI: 0000000000006f71 RDI: 0000000000000004
 RBP: 00007fff409397a0 R08: 0000000000000000 R09: 0000000000000039
 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004006d0
 R13: 00007fff40939880 R14: 0000000000000000 R15: 0000000000000000
  </TASK>
 Kernel panic - not syncing: panic_on_warn set ...

We don't have a NULL check on file_ptr in io_msg_send_fd() function,
so when file_ptr is NUL src_file is also NULL and get_file()
dereferences a NULL pointer and leads to above crash.

Add a NULL check to fix this issue.

Fixes: e6130eba ("io_uring: add support for passing fixed file descriptors")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20221019171218.1337614-1-harshit.m.mogalapalli@oracle.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

If we're invoked with a fixed file, follow the normal rules of not
calling io_fput_file(). Fixed files are permanently registered to the
ring, and do not need putting separately.

Cc: stable@vger.kernel.org
Fixes: aa184e86 ("io_uring: don't attempt to IOPOLL for MSG_RING requests")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We need to make sure (at build time) that struct io_cmd_data is not
casted to a structure that's larger.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Link: https://lore.kernel.org/r/c024cdf25ae19fc0319d4180e2298bade8ed17b8.1660201408.git.metze@samba.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Some use cases of io_post_aux_cqe would not want to overflow as is, but
might want to change the flags/result. For example multishot receive
requires in order CQE, and so if there is an overflow it would need to
stop receiving until the overflow is taken care of.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220630091231.1456789-8-dylany@fb.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

With IORING_OP_MSG_RING, one ring can send a message to another ring.
Extend that support to also allow sending a fixed file descriptor to
that ring, enabling one ring to pass a registered descriptor to another
one.

Arguments are extended to pass in:

sqe->addr3	fixed file slot in source ring
sqe->file_index	fixed file slot in destination ring

IORING_OP_MSG_RING is extended to take a command argument in sqe->addr.
If set to zero (or IORING_MSG_DATA), it sends just a message like before.
If set to IORING_MSG_SEND_FD, a fixed file descriptor is sent according
to the above arguments.

Two common use cases for this are:

1) Server needs to be shutdown or restarted, pass file descriptors to
   another onei

2) Backend is split, and one accepts connections, while others then get
  the fd passed and handle the actual connection.

Both of those are classic SCM_RIGHTS use cases, and it's not possible to
support them with direct descriptors today.

By default, this will post a CQE to the target ring, similarly to how
IORING_MSG_DATA does it. If IORING_MSG_RING_CQE_SKIP is set, no message
is posted to the target ring. The issuer is expected to notify the
receiver side separately.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.h already includes io_uring_types.h, no need to
include it every time. Kill it in a bunch of places, it prepares us for
following patches.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/94d8c943fbe0ef949981c508ddcee7fc1c18850f.1655384063.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Deduplicate some code and add a helper for filling an aux CQE, locking
and notification.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b7c6557c8f9dc5c4cfb01292116c682a0ff61081.1655455613.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Jens Axboe <axboe@kernel.dk>