6.9-stable review patch. If anyone has any objections, please let me know.
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From: Hagar Hemdan hagarhem@amazon.com
[ Upstream commit 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 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 Signed-off-by: Sasha Levin sashal@kernel.org --- io_uring/register.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/io_uring/register.c b/io_uring/register.c index 99c37775f974c..1ae8491e35abb 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))) @@ -381,8 +383,10 @@ 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; }