commit 73254a297c2dd094abec7c9efee32455ae875bdf upstream.

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 mheyne@amazon.de Signed-off-by: Hagar Hemdan hagarhem@amazon.com Link: https://lore.kernel.org/r/20240604130527.3597-1-hagarhem@amazon.com Signed-off-by: Jens Axboe axboe@kernel.dk [Hagar: Modified to apply on v5.15] Signed-off-by: Hagar Hemdan hagarhem@amazon.com --- io_uring/io_uring.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index f1ab0cd98727..3dbc704c7001 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -10818,8 +10818,10 @@ 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))) @@ -10844,8 +10846,11 @@ 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; }