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[ Upstream commit de4eda9de2d957ef2d6a8365a01e26a435e958cb ]
READ/WRITE proved to be actively confusing - the meanings are
"data destination, as used with read(2)" and "data source, as
used with write(2)", but people keep interpreting those as
"we read data from it" and "we write data to it", i.e. exactly
the wrong way.
Call them ITER_DEST and ITER_SOURCE - at least that is harder
to misinterpret...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Stable-dep-of: 6dd88fd59da8 ("vhost-scsi: unbreak any layout for response")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit ef5c600adb1d985513d2b612cc90403a148ff287 ]
Drain requests all go through io_drain_req, which has a quick exit in case
there is nothing pending (ie the drain is not useful). In that case it can
run the issue the request immediately.
However for safety it queues it through task work.
The problem is that in this case the request is run asynchronously, but
the async work has not been prepared through io_req_prep_async.
This has not been a problem up to now, as the task work always would run
before returning to userspace, and so the user would not have a chance to
race with it.
However - with IORING_SETUP_DEFER_TASKRUN - this is no longer the case and
the work might be defered, giving userspace a chance to change data being
referred to in the request.
Instead _always_ prep_async for drain requests, which is simpler anyway
and removes this issue.
Cc: stable@vger.kernel.org
Fixes: c0e0d6ba25f1 ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20230127105911.2420061-1-dylany@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit e276ae344a770f91912a81c6a338d92efd319be2 ]
A preparation patch, make sure we always hold uring_lock around
io_req_complete_failed(). The only place deviating from the rule
is io_cancel_defer_files(), queue a tw instead.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/70760344eadaecf2939287084b9d4ba5c05a6984.1669203009.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: ef5c600adb1d ("io_uring: always prep_async for drain requests")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit f9d567c75ec216447f36da6e855500023504fa04 ]
There is only one user of __io_req_complete_post(), inline it.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ef4c9059950a3da5cf68df00f977f1fd13bd9306.1668597569.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: ef5c600adb1d ("io_uring: always prep_async for drain requests")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit e52d2e583e4ad1d5d0b804d79c2b8752eb0e5ceb ]
__io_req_task_work_add() is huge but marked inline, that makes compilers
to generate lots of garbage. Inline the wrapper caller
io_req_task_work_add() instead.
before and after:
text data bss dec hex filename
47347 16248 8 63603 f873 io_uring/io_uring.o
text data bss dec hex filename
45303 16248 8 61559 f077 io_uring/io_uring.o
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/26dc8c28ca0160e3269ef3e55c5a8b917c4d4450.1668162751.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: ef5c600adb1d ("io_uring: always prep_async for drain requests")
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit b00c51ef8f72ced0965d021a291b98ff822c5337 upstream.
If we're using ring provided buffers with multishot receive, and we end
up doing an io-wq based issue at some points that also needs to select
a buffer, we'll lose the initially assigned buffer group as
io_ring_buffer_select() correctly clears the buffer group list as the
issue isn't serialized by the ctx uring_lock. This is fine for normal
receives as the request puts the buffer and finishes, but for multishot,
we will re-arm and do further receives. On the next trigger for this
multishot receive, the receive will try and pick from a buffer group
whose value is the same as the buffer ID of the las receive. That is
obviously incorrect, and will result in a premature -ENOUFS error for
the receive even if we had available buffers in the correct group.
Cache the buffer group value at prep time, so we can restore it for
future receives. This only needs doing for the above mentioned case, but
just do it by default to keep it easier to read.
Cc: stable@vger.kernel.org
Fixes: b3fdea6ecb55 ("io_uring: multishot recv")
Fixes: 9bb66906f23e ("io_uring: support multishot in recvmsg")
Cc: Dylan Yudaken <dylany@meta.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 8579538c89e33ce78be2feb41e07489c8cbf8f31 upstream.
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: 6d043ee1164ca ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 8caa03f10bf92cb8657408a6ece6a8a73f96ce13 upstream.
A previous commit fixed a poll race that can occur, but it's only
applicable for multishot requests. For a multishot request, we can safely
ignore a spurious wakeup, as we never leave the waitqueue to begin with.
A blunt reissue of a multishot armed request can cause us to leak a
buffer, if they are ring provided. While this seems like a bug in itself,
it's not really defined behavior to reissue a multishot request directly.
It's less efficient to do so as well, and not required to rearm anything
like it is for singleshot poll requests.
Cc: stable@vger.kernel.org
Fixes: 6e5aedb9324a ("io_uring/poll: attempt request issue after racy poll wakeup")
Reported-and-tested-by: Olivier Langlois <olivier@trillion01.com>
Link: https://github.com/axboe/liburing/issues/778
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit e6db6f9398dadcbc06318a133d4c44a2d3844e61 upstream.
We have two types of task_work based creation, one is using an existing
worker to setup a new one (eg when going to sleep and we have no free
workers), and the other is allocating a new worker. Only the latter
should be freed when we cancel task_work creation for a new worker.
Fixes: af82425c6a2d ("io_uring/io-wq: free worker if task_work creation is canceled")
Reported-by: syzbot+d56ec896af3637bdb7e4@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit af82425c6a2d2f347c79b63ce74fca6dc6be157f upstream.
If we cancel the task_work, the worker will never come into existance.
As this is the last reference to it, ensure that we get it freed
appropriately.
Cc: stable@vger.kernel.org
Reported-by: 진호 <wnwlsgh98@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 6e5aedb9324aab1c14a23fae3d8eeb64a679c20e upstream.
If we have multiple requests waiting on the same target poll waitqueue,
then it's quite possible to get a request triggered and get disappointed
in not being able to make any progress with it. If we race in doing so,
we'll potentially leave the poll request on the internal tables, but
removed from the waitqueue. That means that any subsequent trigger of
the poll waitqueue will not kick that request into action, causing an
application to potentially wait for completion of a request that will
never happen.
Fix this by adding a new poll return state, IOU_POLL_REISSUE. Rather
than have complicated logic for how to re-arm a given type of request,
just punt it for a reissue.
While in there, move the 'ret' variable to the only section where it
gets used. This avoids confusion the scope of it.
Cc: stable@vger.kernel.org
Fixes: eb0089d629ba ("io_uring: single shot poll removal optimisation")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 544d163d659d45a206d8929370d5a2984e546cb7 upstream.
syzbot reports an issue with overflow filling for IOPOLL:
WARNING: CPU: 0 PID: 28 at io_uring/io_uring.c:734 io_cqring_event_overflow+0x1c0/0x230 io_uring/io_uring.c:734
CPU: 0 PID: 28 Comm: kworker/u4:1 Not tainted 6.2.0-rc3-syzkaller-16369-g358a161a6a9e #0
Workqueue: events_unbound io_ring_exit_work
Call trace:
io_cqring_event_overflow+0x1c0/0x230 io_uring/io_uring.c:734
io_req_cqe_overflow+0x5c/0x70 io_uring/io_uring.c:773
io_fill_cqe_req io_uring/io_uring.h:168 [inline]
io_do_iopoll+0x474/0x62c io_uring/rw.c:1065
io_iopoll_try_reap_events+0x6c/0x108 io_uring/io_uring.c:1513
io_uring_try_cancel_requests+0x13c/0x258 io_uring/io_uring.c:3056
io_ring_exit_work+0xec/0x390 io_uring/io_uring.c:2869
process_one_work+0x2d8/0x504 kernel/workqueue.c:2289
worker_thread+0x340/0x610 kernel/workqueue.c:2436
kthread+0x12c/0x158 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:863
There is no real problem for normal IOPOLL as flush is also called with
uring_lock taken, but it's getting more complicated for IOPOLL|SQPOLL,
for which __io_cqring_overflow_flush() happens from the CQ waiting path.
Reported-and-tested-by: syzbot+6805087452d72929404e@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit ea97cbebaf861d99c3e892275147e6fca6d2c1ca upstream.
A previous commit split the hash table for polled requests into two
parts, but didn't get the fdinfo output updated. This means that it's
less useful for debugging, as we may think a given request is not pending
poll.
Fix this up by dumping the locked hash table contents too.
Fixes: 9ca9fb24d5fe ("io_uring: mutex locked poll hashing")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit febb985c06cb6f5fac63598c0bffd4fd823d110d upstream.
If we don't, then we may lose access to it completely, leading to a
request leak. This will eventually stall the ring exit process as
well.
Cc: stable@vger.kernel.org
Fixes: 49f1c68e048f ("io_uring: optimise submission side poll_refs")
Reported-and-tested-by: syzbot+6c95df01470a47fc3af4@syzkaller.appspotmail.com
Link: https://lore.kernel.org/io-uring/0000000000009f829805f1ce87b2@google.com/
Suggested-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 12521a5d5cb7ff0ad43eadfc9c135d86e1131fa8 upstream.
Jiffy to ktime CQ waiting conversion broke how we treat timeouts, in
particular we rearm it anew every time we get into
io_cqring_wait_schedule() without adjusting the timeout. Waiting for 2
CQEs and getting a task_work in the middle may double the timeout value,
or even worse in some cases task may wait indefinitely.
Cc: stable@vger.kernel.org
Fixes: 228339662b398 ("io_uring: don't convert to jiffies for waiting on timeouts")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f7bffddd71b08f28a877d44d37ac953ddb01590d.1672915663.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 9ffa13ff78a0a55df968a72d6f0ebffccee5c9f4 upstream.
Unlike normal tw, nothing prevents deferred tw to be executed right
after an tw item added to ->work_llist in io_req_local_work_add(). For
instance, the waiting task may get waken up by CQ posting or a normal
tw. Thus we need to pin the ring for the rest of io_req_local_work_add()
Cc: stable@vger.kernel.org
Fixes: c0e0d6ba25f18 ("io_uring: add IORING_SETUP_DEFER_TASKRUN")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1a79362b9c10b8523ef70b061d96523650a23344.1672795998.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 343190841a1f22b96996d9f8cfab902a4d1bfd0e ]
We only check the register opcode value inside the restricted ring
section, move it into the main io_uring_register() function instead
and check it up front.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 23fffb2f09ce1145cbd751801d45ba74acaa6542 ]
If we have a signal pending during cancelations, it'll cause the
task_work run to return an error. Since we didn't run task_work, the
current task is left in TASK_INTERRUPTIBLE state when we need to
re-grab the ctx mutex, and the kernel will rightfully complain about
that.
Move the lock grabbing for the error cases outside the loop to avoid
that issue.
Reported-by: syzbot+7df055631cd1be4586fd@syzkaller.appspotmail.com
Link: https://lore.kernel.org/io-uring/0000000000003a14a905f05050b0@google.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 4464853277d0ccdb9914608dd1332f0fa2f9846f ]
Pass in EPOLL_URING_WAKE when signaling eventfd or doing poll related
wakups, so that we can check for a circular event dependency between
eventfd and epoll. If this flag is set when our wakeup handlers are
called, then we know we have a dependency that needs to terminate
multishot requests.
eventfd and epoll are the only such possible dependencies.
Cc: stable@vger.kernel.org # 6.0
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 2dac1a159216b39ced8d78dba590c5d2f4249586 upstream.
This reverts commit 2ccc92f4effcfa1c51c4fcf1e34d769099d3cad4
io_req_complete_post() should now behave well even in case of IOPOLL, we
can remove completion_lock locking.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7e171c8b530656b14a671c59100ca260e46e7f2a.1669203009.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit ea011ee10231f5fa6cbb415007048ca0bb948baf upstream.
Read cq_timeouts in io_flush_timeouts() only after taking the
timeout_lock, as it's protected by it. There are many places where we
also grab ->completion_lock, but for instance io_timeout_fn() doesn't
and still modifies cq_timeouts.
Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9c79544dd6cf5c4018cb1bab99cf481a93ea46ef.1670002973.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 990a4de57e44f4f4cfc33c90d2ec5d285b7c8342 upstream.
If we're not allocating the vectors because the count is below
UIO_FASTIOV, we still do need to properly clear ->free_iov to prevent
an erronous free of on-stack data.
Reported-by: Jiri Slaby <jirislaby@gmail.com>
Fixes: 4c17a496a7a0 ("io_uring/net: fix cleanup double free free_iov init")
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit ef0ec1ad03119b8b46b035dad42bca7d6da7c2e5 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Syzkaller reports a NULL deref bug as follows:
BUG: KASAN: null-ptr-deref in io_tctx_exit_cb+0x53/0xd3
Read of size 4 at addr 0000000000000138 by task file1/1955
CPU: 1 PID: 1955 Comm: file1 Not tainted 6.1.0-rc7-00103-gef4d3ea40565 #75
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xcd/0x134
? io_tctx_exit_cb+0x53/0xd3
kasan_report+0xbb/0x1f0
? io_tctx_exit_cb+0x53/0xd3
kasan_check_range+0x140/0x190
io_tctx_exit_cb+0x53/0xd3
task_work_run+0x164/0x250
? task_work_cancel+0x30/0x30
get_signal+0x1c3/0x2440
? lock_downgrade+0x6e0/0x6e0
? lock_downgrade+0x6e0/0x6e0
? exit_signals+0x8b0/0x8b0
? do_raw_read_unlock+0x3b/0x70
? do_raw_spin_unlock+0x50/0x230
arch_do_signal_or_restart+0x82/0x2470
? kmem_cache_free+0x260/0x4b0
? putname+0xfe/0x140
? get_sigframe_size+0x10/0x10
? do_execveat_common.isra.0+0x226/0x710
? lockdep_hardirqs_on+0x79/0x100
? putname+0xfe/0x140
? do_execveat_common.isra.0+0x238/0x710
exit_to_user_mode_prepare+0x15f/0x250
syscall_exit_to_user_mode+0x19/0x50
do_syscall_64+0x42/0xb0
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0023:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 002b:00000000fffb7790 EFLAGS: 00000200 ORIG_RAX: 000000000000000b
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Kernel panic - not syncing: panic_on_warn set ...
This happens because the adding of task_work from io_ring_exit_work()
isn't synchronized with canceling all work items from eg exec. The
execution of the two are ordered in that they are both run by the task
itself, but if io_tctx_exit_cb() is queued while we're canceling all
work items off exec AND gets executed when the task exits to userspace
rather than in the main loop in io_uring_cancel_generic(), then we can
find current->io_uring == NULL and hit the above crash.
It's safe to add this NULL check here, because the execution of the two
paths are done by the task itself.
Cc: stable@vger.kernel.org
Fixes: d56d938b4bef ("io_uring: do ctx initiated file note removal")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20221206093833.3812138-1-harshit.m.mogalapalli@oracle.com
[axboe: add code comment and also put an explanation in the commit msg]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With how task_work is added and signaled, we can have TIF_NOTIFY_SIGNAL
set and no task_work pending as it got run in a previous loop. Treat
TIF_NOTIFY_SIGNAL like get_signal(), always clear it if set regardless
of whether or not task_work is pending to run.
Cc: stable@vger.kernel.org
Fixes: 46a525e199e4 ("io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There is an interesting race condition of poll_refs which could result
in a NULL pointer dereference. The crash trace is like:
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 PID: 30781 Comm: syz-executor.2 Not tainted 6.0.0-g493ffd6605b2 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:io_poll_remove_entry io_uring/poll.c:154 [inline]
RIP: 0010:io_poll_remove_entries+0x171/0x5b4 io_uring/poll.c:190
Code: ...
RSP: 0018:ffff88810dfefba0 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000040000
RDX: ffffc900030c4000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: 0000000000000008 R08: ffffffff9764d3dd R09: fffffbfff3836781
R10: fffffbfff3836781 R11: 0000000000000000 R12: 1ffff11003422d60
R13: ffff88801a116b04 R14: ffff88801a116ac0 R15: dffffc0000000000
FS: 00007f9c07497700(0000) GS:ffff88811a600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffb5c00ea98 CR3: 0000000105680005 CR4: 0000000000770ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
<TASK>
io_apoll_task_func+0x3f/0xa0 io_uring/poll.c:299
handle_tw_list io_uring/io_uring.c:1037 [inline]
tctx_task_work+0x37e/0x4f0 io_uring/io_uring.c:1090
task_work_run+0x13a/0x1b0 kernel/task_work.c:177
get_signal+0x2402/0x25a0 kernel/signal.c:2635
arch_do_signal_or_restart+0x3b/0x660 arch/x86/kernel/signal.c:869
exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
exit_to_user_mode_prepare+0xc2/0x160 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
syscall_exit_to_user_mode+0x58/0x160 kernel/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The root cause for this is a tiny overlooking in
io_poll_check_events() when cocurrently run with poll cancel routine
io_poll_cancel_req().
The interleaving to trigger use-after-free:
CPU0 | CPU1
|
io_apoll_task_func() | io_poll_cancel_req()
io_poll_check_events() |
// do while first loop |
v = atomic_read(...) |
// v = poll_refs = 1 |
... | io_poll_mark_cancelled()
| atomic_or()
| // poll_refs =
IO_POLL_CANCEL_FLAG | 1
|
atomic_sub_return(...) |
// poll_refs = IO_POLL_CANCEL_FLAG |
// loop continue |
|
| io_poll_execute()
| io_poll_get_ownership()
| // poll_refs =
IO_POLL_CANCEL_FLAG | 1
| // gets the ownership
v = atomic_read(...) |
// poll_refs not change |
|
if (v & IO_POLL_CANCEL_FLAG) |
return -ECANCELED; |
// io_poll_check_events return |
// will go into |
// io_req_complete_failed() free req |
|
| io_apoll_task_func()
| // also go into
io_req_complete_failed()
And the interleaving to trigger the kernel WARNING:
CPU0 | CPU1
|
io_apoll_task_func() | io_poll_cancel_req()
io_poll_check_events() |
// do while first loop |
v = atomic_read(...) |
// v = poll_refs = 1 |
... | io_poll_mark_cancelled()
| atomic_or()
| // poll_refs =
IO_POLL_CANCEL_FLAG | 1
|
atomic_sub_return(...) |
// poll_refs = IO_POLL_CANCEL_FLAG |
// loop continue |
|
v = atomic_read(...) |
// v = IO_POLL_CANCEL_FLAG |
| io_poll_execute()
| io_poll_get_ownership()
| // poll_refs =
IO_POLL_CANCEL_FLAG | 1
| // gets the ownership
|
WARN_ON_ONCE(!(v & IO_POLL_REF_MASK))) |
// v & IO_POLL_REF_MASK = 0 WARN |
|
| io_apoll_task_func()
| // also go into
io_req_complete_failed()
By looking up the source code and communicating with Pavel, the
implementation of this atomic poll refs should continue the loop of
io_poll_check_events() just to avoid somewhere else to grab the
ownership. Therefore, this patch simply adds another AND operation to
make sure the loop will stop if it finds the poll_refs is exactly equal
to IO_POLL_CANCEL_FLAG. Since io_poll_cancel_req() grabs ownership and
will finally make its way to io_req_complete_failed(), the req will
be reclaimed as expected.
Fixes: aa43477b0402 ("io_uring: poll rework")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: tweak description and code style]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There is an interesting reference bug when -ENOMEM occurs in calling of
io_install_fixed_file(). KASan report like below:
[ 14.057131] ==================================================================
[ 14.059161] BUG: KASAN: use-after-free in unix_get_socket+0x10/0x90
[ 14.060975] Read of size 8 at addr ffff88800b09cf20 by task kworker/u8:2/45
[ 14.062684]
[ 14.062768] CPU: 2 PID: 45 Comm: kworker/u8:2 Not tainted 6.1.0-rc4 #1
[ 14.063099] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
[ 14.063666] Workqueue: events_unbound io_ring_exit_work
[ 14.063936] Call Trace:
[ 14.064065] <TASK>
[ 14.064175] dump_stack_lvl+0x34/0x48
[ 14.064360] print_report+0x172/0x475
[ 14.064547] ? _raw_spin_lock_irq+0x83/0xe0
[ 14.064758] ? __virt_addr_valid+0xef/0x170
[ 14.064975] ? unix_get_socket+0x10/0x90
[ 14.065167] kasan_report+0xad/0x130
[ 14.065353] ? unix_get_socket+0x10/0x90
[ 14.065553] unix_get_socket+0x10/0x90
[ 14.065744] __io_sqe_files_unregister+0x87/0x1e0
[ 14.065989] ? io_rsrc_refs_drop+0x1c/0xd0
[ 14.066199] io_ring_exit_work+0x388/0x6a5
[ 14.066410] ? io_uring_try_cancel_requests+0x5bf/0x5bf
[ 14.066674] ? try_to_wake_up+0xdb/0x910
[ 14.066873] ? virt_to_head_page+0xbe/0xbe
[ 14.067080] ? __schedule+0x574/0xd20
[ 14.067273] ? read_word_at_a_time+0xe/0x20
[ 14.067492] ? strscpy+0xb5/0x190
[ 14.067665] process_one_work+0x423/0x710
[ 14.067879] worker_thread+0x2a2/0x6f0
[ 14.068073] ? process_one_work+0x710/0x710
[ 14.068284] kthread+0x163/0x1a0
[ 14.068454] ? kthread_complete_and_exit+0x20/0x20
[ 14.068697] ret_from_fork+0x22/0x30
[ 14.068886] </TASK>
[ 14.069000]
[ 14.069088] Allocated by task 289:
[ 14.069269] kasan_save_stack+0x1e/0x40
[ 14.069463] kasan_set_track+0x21/0x30
[ 14.069652] __kasan_slab_alloc+0x58/0x70
[ 14.069899] kmem_cache_alloc+0xc5/0x200
[ 14.070100] __alloc_file+0x20/0x160
[ 14.070283] alloc_empty_file+0x3b/0xc0
[ 14.070479] path_openat+0xc3/0x1770
[ 14.070689] do_filp_open+0x150/0x270
[ 14.070888] do_sys_openat2+0x113/0x270
[ 14.071081] __x64_sys_openat+0xc8/0x140
[ 14.071283] do_syscall_64+0x3b/0x90
[ 14.071466] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 14.071791]
[ 14.071874] Freed by task 0:
[ 14.072027] kasan_save_stack+0x1e/0x40
[ 14.072224] kasan_set_track+0x21/0x30
[ 14.072415] kasan_save_free_info+0x2a/0x50
[ 14.072627] __kasan_slab_free+0x106/0x190
[ 14.072858] kmem_cache_free+0x98/0x340
[ 14.073075] rcu_core+0x427/0xe50
[ 14.073249] __do_softirq+0x110/0x3cd
[ 14.073440]
[ 14.073523] Last potentially related work creation:
[ 14.073801] kasan_save_stack+0x1e/0x40
[ 14.074017] __kasan_record_aux_stack+0x97/0xb0
[ 14.074264] call_rcu+0x41/0x550
[ 14.074436] task_work_run+0xf4/0x170
[ 14.074619] exit_to_user_mode_prepare+0x113/0x120
[ 14.074858] syscall_exit_to_user_mode+0x1d/0x40
[ 14.075092] do_syscall_64+0x48/0x90
[ 14.075272] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 14.075529]
[ 14.075612] Second to last potentially related work creation:
[ 14.075900] kasan_save_stack+0x1e/0x40
[ 14.076098] __kasan_record_aux_stack+0x97/0xb0
[ 14.076325] task_work_add+0x72/0x1b0
[ 14.076512] fput+0x65/0xc0
[ 14.076657] filp_close+0x8e/0xa0
[ 14.076825] __x64_sys_close+0x15/0x50
[ 14.077019] do_syscall_64+0x3b/0x90
[ 14.077199] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 14.077448]
[ 14.077530] The buggy address belongs to the object at ffff88800b09cf00
[ 14.077530] which belongs to the cache filp of size 232
[ 14.078105] The buggy address is located 32 bytes inside of
[ 14.078105] 232-byte region [ffff88800b09cf00, ffff88800b09cfe8)
[ 14.078685]
[ 14.078771] The buggy address belongs to the physical page:
[ 14.079046] page:000000001bd520e7 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88800b09de00 pfn:0xb09c
[ 14.079575] head:000000001bd520e7 order:1 compound_mapcount:0 compound_pincount:0
[ 14.079946] flags: 0x100000000010200(slab|head|node=0|zone=1)
[ 14.080244] raw: 0100000000010200 0000000000000000 dead000000000001 ffff88800493cc80
[ 14.080629] raw: ffff88800b09de00 0000000080190018 00000001ffffffff 0000000000000000
[ 14.081016] page dumped because: kasan: bad access detected
[ 14.081293]
[ 14.081376] Memory state around the buggy address:
[ 14.081618] ffff88800b09ce00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 14.081974] ffff88800b09ce80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
[ 14.082336] >ffff88800b09cf00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[ 14.082690] ^
[ 14.082909] ffff88800b09cf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
[ 14.083266] ffff88800b09d000: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
[ 14.083622] ==================================================================
The actual tracing of this bug is shown below:
commit 8c71fe750215 ("io_uring: ensure fput() called correspondingly
when direct install fails") adds an additional fput() in
io_fixed_fd_install() when io_file_bitmap_get() returns error values. In
that case, the routine will never make it to io_install_fixed_file() due
to an early return.
static int io_fixed_fd_install(...)
{
if (alloc_slot) {
...
ret = io_file_bitmap_get(ctx);
if (unlikely(ret < 0)) {
io_ring_submit_unlock(ctx, issue_flags);
fput(file);
return ret;
}
...
}
...
ret = io_install_fixed_file(req, file, issue_flags, file_slot);
...
}
In the above scenario, the reference is okay as io_fixed_fd_install()
ensures the fput() is called when something bad happens, either via
bitmap or via inner io_install_fixed_file().
However, the commit 61c1b44a21d7 ("io_uring: fix deadlock on iowq file
slot alloc") breaks the balance because it places fput() into the common
path for both io_file_bitmap_get() and io_install_fixed_file(). Since
io_install_fixed_file() handles the fput() itself, the reference
underflow come across then.
There are some extra commits make the current code into
io_fixed_fd_install() -> __io_fixed_fd_install() ->
io_install_fixed_file()
However, the fact that there is an extra fput() is called if
io_install_fixed_file() calls fput(). Traversing through the code, I
find that the existing two callers to __io_fixed_fd_install():
io_fixed_fd_install() and io_msg_send_fd() have fput() when handling
error return, this patch simply removes the fput() in
io_install_fixed_file() to fix the bug.
Fixes: 61c1b44a21d7 ("io_uring: fix deadlock on iowq file slot alloc")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Link: https://lore.kernel.org/r/be4ba4b.5d44.184a0a406a4.Coremail.linma@zju.edu.cn
Signed-off-by: Jens Axboe <axboe@kernel.dk>
poll_refs carry two functions, the first is ownership over the request.
The second is notifying the io_poll_check_events() that there was an
event but wake up couldn't grab the ownership, so io_poll_check_events()
should retry.
We want to make poll_refs more robust against overflows. Instead of
always incrementing it, which covers two purposes with one atomic, check
if poll_refs is elevated enough and if so set a retry flag without
attempts to grab ownership. The gap between the bias check and following
atomics may seem racy, but we don't need it to be strict. Moreover there
might only be maximum 4 parallel updates: by the first and the second
poll entries, __io_arm_poll_handler() and cancellation. From those four,
only poll wake ups may be executed multiple times, but they're protected
by a spin.
Cc: stable@vger.kernel.org
Reported-by: Lin Ma <linma@zju.edu.cn>
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c762bc31f8683b3270f3587691348a7119ef9c9d.1668963050.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Replace atomically substracting the ownership reference at the end of
arming a poll with a cmpxchg. We try to release ownership by setting 0
assuming that poll_refs didn't change while we were arming. If it did
change, we keep the ownership and use it to queue a tw, which is fully
capable to process all events and (even tolerates spurious wake ups).
It's a bit more elegant as we reduce races b/w setting the cancellation
flag and getting refs with this release, and with that we don't have to
worry about any kinds of underflows. It's not the fastest path for
polling. The performance difference b/w cmpxchg and atomic dec is
usually negligible and it's not the fastest path.
Cc: stable@vger.kernel.org
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/0c95251624397ea6def568ff040cad2d7926fd51.1668963050.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When we post a CQE we wake all ring pollers as it normally should be.
However, if a CQE was generated by a multishot poll request targeting
its own ring, it'll wake that request up, which will make it to post
a new CQE, which will wake the request and so on until it exhausts all
CQ entries.
Don't allow multishot polling io_uring files but downgrade them to
oneshots, which was always stated as a correct behaviour that the
userspace should check for.
Cc: stable@vger.kernel.org
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3124038c0e7474d427538c2d915335ec28c92d21.1668785722.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Having REQ_F_POLLED set doesn't guarantee that the request is
executed as a multishot from the polling path. Fortunately for us, if
the code thinks it's multishot issue when it's not, it can only ask to
skip completion so leaking the request. Use issue_flags to mark
multipoll issues.
Cc: stable@vger.kernel.org
Fixes: 1300ebb20286b ("io_uring: multishot recv")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/37762040ba9c52b81b92a2f5ebfd4ee484088951.1668710222.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Having REQ_F_POLLED set doesn't guarantee that the request is
executed as a multishot from the polling path. Fortunately for us, if
the code thinks it's multishot issue when it's not, it can only ask to
skip completion so leaking the request. Use issue_flags to mark
multipoll issues.
Cc: stable@vger.kernel.org
Fixes: 390ed29b5e425 ("io_uring: add IORING_ACCEPT_MULTISHOT for accept")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7700ac57653f2823e30b34dc74da68678c0c5f13.1668710222.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When io_poll_check_events() collides with someone attempting to queue a
task work, it'll spin for one more time. However, it'll continue to use
the mask from the first iteration instead of updating it. For example,
if the first wake up was a EPOLLIN and the second EPOLLOUT, the
userspace will not get EPOLLOUT in time.
Clear the mask for all subsequent iterations to force vfs_poll().
Cc: stable@vger.kernel.org
Fixes: aa43477b04025 ("io_uring: poll rework")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2dac97e8f691231049cb259c4ae57e79e40b537c.1668710222.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
io_poll_double_prepare() | io_poll_wake()
| poll->head = NULL
smp_load(&poll->head); /* NULL */ |
flags = req->flags; |
| req->flags &= ~SINGLE_POLL;
req->flags = flags | DOUBLE_POLL |
The idea behind io_poll_double_prepare() is to serialise with the
first poll entry by taking the wq lock. However, it's not safe to assume
that io_poll_wake() is not running when we can't grab the lock and so we
may race modifying req->flags.
Skip double poll setup if that happens. It's ok because the first poll
entry will only be removed when it's definitely completing, e.g.
pollfree or oneshot with a valid mask.
Fixes: 49f1c68e048f1 ("io_uring: optimise submission side poll_refs")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b7fab2d502f6121a7d7b199fe4d914a43ca9cdfd.1668184658.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We already check if the chosen starting offset for the buffer IDs fit
within an unsigned short, as 65535 is the maximum value for a provided
buffer. But if the caller asks to add N buffers at offset M, and M + N
would exceed the size of the unsigned short, we simply add buffers with
wrapping around the ID.
This is not necessarily a bug and could in fact be a valid use case, but
it seems confusing and inconsistent with the initial check for starting
offset. Let's check for wrap consistently, and error the addition if we
do need to wrap.
Reported-by: Olivier Langlois <olivier@trillion01.com>
Link: https://github.com/axboe/liburing/issues/726
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
io_cqring_wait (and it's wake function io_has_work) used cached_cq_tail in
order to calculate the number of CQEs. cached_cq_tail is set strictly
before the user visible rings->cq.tail
However as far as userspace is concerned, if io_uring_enter(2) is called
with a minimum number of events, they will verify by checking
rings->cq.tail.
It is therefore possible for io_uring_enter(2) to return early with fewer
events visible to the user.
Instead make the wait functions read from the user visible value, so there
will be no discrepency.
This is triggered eventually by the following reproducer:
struct io_uring_sqe *sqe;
struct io_uring_cqe *cqe;
unsigned int cqe_ready;
struct io_uring ring;
int ret, i;
ret = io_uring_queue_init(N, &ring, 0);
assert(!ret);
while(true) {
for (i = 0; i < N; i++) {
sqe = io_uring_get_sqe(&ring);
io_uring_prep_nop(sqe);
sqe->flags |= IOSQE_ASYNC;
}
ret = io_uring_submit(&ring);
assert(ret == N);
do {
ret = io_uring_wait_cqes(&ring, &cqe, N, NULL, NULL);
} while(ret == -EINTR);
cqe_ready = io_uring_cq_ready(&ring);
assert(!ret);
assert(cqe_ready == N);
io_uring_cq_advance(&ring, N);
}
Fixes: ad3eb2c89fb2 ("io_uring: split overflow state into SQ and CQ side")
Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221108153016.1854297-1-dylany@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It is possible for tw to lock the ring, and this was not propogated out to
io_run_local_work. This can cause an unlock to be missed.
Instead pass a pointer to locked into __io_run_local_work.
Fixes: 8ac5d85a89b4 ("io_uring: add local task_work run helper that is entered locked")
Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221027144429.3971400-3-dylany@meta.com
[axboe: WARN_ON() -> WARN_ON_ONCE() and add a minor comment]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If a protocol doesn't support zerocopy it will silently fall back to
copying. This type of behaviour has always been a source of troubles
so it's better to fail such requests instead.
Cc: <stable@vger.kernel.org> # 6.0
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2db3c7f16bb6efab4b04569cd16e6242b40c5cb3.1666346426.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If the CPU mask allocation for a node fails, then the memory allocated for
the 'io_wqe' struct of the current node doesn't get freed on the error
handling path, since it has not yet been added to the 'wqes' array.
This was spotted when fuzzing v6.1-rc1 with Syzkaller:
BUG: memory leak
unreferenced object 0xffff8880093d5000 (size 1024):
comm "syz-executor.2", pid 7701, jiffies 4295048595 (age 13.900s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<00000000cb463369>] __kmem_cache_alloc_node+0x18e/0x720
[<00000000147a3f9c>] kmalloc_node_trace+0x2a/0x130
[<000000004e107011>] io_wq_create+0x7b9/0xdc0
[<00000000c38b2018>] io_uring_alloc_task_context+0x31e/0x59d
[<00000000867399da>] __io_uring_add_tctx_node.cold+0x19/0x1ba
[<000000007e0e7a79>] io_uring_setup.cold+0x1b80/0x1dce
[<00000000b545e9f6>] __x64_sys_io_uring_setup+0x5d/0x80
[<000000008a8a7508>] do_syscall_64+0x5d/0x90
[<000000004ac08bec>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
Fixes: 0e03496d1967 ("io-wq: use private CPU mask")
Cc: stable@vger.kernel.org
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Link: https://lore.kernel.org/r/20221020014710.902201-1-rafaelmendsr@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
