From 73254a297c2dd094abec7c9efee32455ae875bdf Mon Sep 17 00:00:00 2001 From: Hagar Hemdan Date: Tue, 4 Jun 2024 13:05:27 +0000 Subject: io_uring: fix possible deadlock in io_register_iowq_max_workers() 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 009ad9f0c6ee ("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: Maximilian Heyne Signed-off-by: Hagar Hemdan Link: https://lore.kernel.org/r/20240604130527.3597-1-hagarhem@amazon.com Signed-off-by: Jens Axboe --- io_uring/register.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'io_uring') diff --git a/io_uring/register.c b/io_uring/register.c index ef8c908346a4..c0010a66a6f2 100644 --- a/io_uring/register.c +++ b/io_uring/register.c @@ -355,8 +355,10 @@ static __cold 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))) @@ -380,8 +382,10 @@ static __cold 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; } -- cgit v1.2.3