From: Hagar Hemdan Date: Tue, 4 Jun 2024 13:05:27 +0000 (+0000) Subject: io_uring: fix possible deadlock in io_register_iowq_max_workers() X-Git-Tag: v5.15.173~6 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=97ed7ff58de66c544692b3c2b988f3f594348de0;p=thirdparty%2Fkernel%2Fstable.git io_uring: fix possible deadlock in io_register_iowq_max_workers() 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 Signed-off-by: Hagar Hemdan Link: https://lore.kernel.org/r/20240604130527.3597-1-hagarhem@amazon.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index b53099b595cc7..43dd54c576d68 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -10822,8 +10822,10 @@ 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))) @@ -10848,8 +10850,11 @@ 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; }