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@xxxxxxxxx>
Signed-off-by: Hagar Hemdan <hagarhem@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240604130527.3597-1-hagarhem@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
[Hagar: Modified to apply on v6.1]
Signed-off-by: Hagar Hemdan <hagarhem@xxxxxxxxxx>
---
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 92c1aa8f3501..4f0ae938b146 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3921,8 +3921,10 @@ 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)))
@@ -3947,8 +3949,11 @@ 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;
}
--
2.40.1
