Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
io_uring/timeout: annotate data race in io_flush_timeouts()
syzbot correctly reports this as a KCSAN race, as ctx->cached_cq_tail
should be read under ->uring_lock. This isn't immediately feasible in
io_flush_timeouts(), but as long as we read a stable value, that should
be good enough. If two io-wq threads compete on this value, then they
will both end up calling io_flush_timeouts() and at least one of them
will see the correct value.
Reported-by: syzbot+6c48db7d94402407301e@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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io_uring/timeout.c
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io_uring/timeout.c
···
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u32 seq;
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raw_spin_lock_irq(&ctx->timeout_lock);
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-
seq = ctx->cached_cq_tail - atomic_read(&ctx->cq_timeouts);
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+
seq = READ_ONCE(ctx->cached_cq_tail) - atomic_read(&ctx->cq_timeouts);
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list_for_each_entry_safe(timeout, tmp, &ctx->timeout_list, list) {
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struct io_kiocb *req = cmd_to_io_kiocb(timeout);