Commit 542b8f05 authored by Hagar Hemdan's avatar Hagar Hemdan Committed by Wang Zhaolong
Browse files

io_uring: fix possible deadlock in io_register_iowq_max_workers() 

mainline inclusion
from mainline-v6.10-rc3
commit 73254a297c2dd094abec7c9efee32455ae875bdf
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAGEK8
CVE: CVE-2024-41080

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=73254a297c2dd094abec7c9efee32455ae875bdf



--------------------------------

The io_register_iowq_max_workers() function calls io_put_sq_data(),
which acquires the sqd->lock without releasing the uring_lock.
Similar to the commit 009ad9f0 ("io_uring: drop ctx->uring_lock
before acquiring sqd->lock"), this can lead to a potential deadlock
situation.

To resolve this issue, the uring_lock is released before calling
io_put_sq_data(), and then it is re-acquired after the function call.

This change ensures that the locks are acquired in the correct
order, preventing the possibility of a deadlock.

Suggested-by: default avatarMaximilian Heyne <mheyne@amazon.de>
Signed-off-by: default avatarHagar Hemdan <hagarhem@amazon.com>
Link: https://lore.kernel.org/r/20240604130527.3597-1-hagarhem@amazon.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Conflicts:
    io_uring/io_uring.c
    io_uring/register.c
[Commit c43203154d8ac moves related functions from io_uring/io_uring.c
to io_uring/register.c.]
Signed-off-by: default avatarWang Zhaolong <wangzhaolong1@huawei.com>
parent 98dea376

io_uring/io_uring.c

+4 −0
Original line number Diff line number Diff line
@@ -10637,8 +10637,10 @@ static int io_register_iowq_max_workers(struct io_ring_ctx *ctx, 
	}



	if (sqd) {

		mutex_unlock(&ctx->uring_lock);

		mutex_unlock(&sqd->lock);

		io_put_sq_data(sqd);

		mutex_lock(&ctx->uring_lock);

	}



	if (copy_to_user(arg, new_count, sizeof(new_count)))
@@ -10663,8 +10665,10 @@ static int io_register_iowq_max_workers(struct io_ring_ctx *ctx, 
	return 0;

err:

	if (sqd) {

		mutex_unlock(&ctx->uring_lock);

		mutex_unlock(&sqd->lock);

		io_put_sq_data(sqd);

		mutex_lock(&ctx->uring_lock);

	}

	return ret;

}