6.6-stable review patch. If anyone has any objections, please let me know.
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From: Hagar Hemdan hagarhem@amazon.com
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io_uring.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -4358,8 +4358,10 @@ static __cold int io_register_iowq_max_w }
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))) @@ -4384,8 +4386,11 @@ static __cold int io_register_iowq_max_w 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; }