[v1] md: fix potential NULL pointer dereference in md_super_write

[PATCH] md: fix potential NULL pointer dereference in md_super_write

Posted by Ye Chey 6 months, 3 weeks ago

The bio_alloc_bioset() call in md_super_write() could fail under memory
pressure and return NULL. Add a check to handle this case gracefully by
returning early, preventing a potential NULL pointer dereference.

Signed-off-by: Ye Chey <yechey@ai-sast.com>
---
 drivers/md/md.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9daa78c5f..a0e2d90d4 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1002,6 +1002,8 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
 			      REQ_OP_WRITE | REQ_SYNC | REQ_IDLE | REQ_META
 				  | REQ_PREFLUSH | REQ_FUA,
 			      GFP_NOIO, &mddev->sync_set);
+	if (!bio)
+		return;
 
 	atomic_inc(&rdev->nr_pending);
 
-- 
2.44.0

Re: [PATCH] md: fix potential NULL pointer dereference in md_super_write

Posted by Yu Kuai 6 months, 3 weeks ago

Hi,

在 2025/05/23 17:35, Ye Chey 写道:
> The bio_alloc_bioset() call in md_super_write() could fail under memory
> pressure and return NULL. Add a check to handle this case gracefully by
> returning early, preventing a potential NULL pointer dereference.

NAK, if you read the comments of bio_alloc_bioset(), you'll know there
are cases bio_alloc_bioset() will never return NULL.

Thanks,
Kuai

> 
> Signed-off-by: Ye Chey <yechey@ai-sast.com>
> ---
>   drivers/md/md.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9daa78c5f..a0e2d90d4 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1002,6 +1002,8 @@ void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
>   			      REQ_OP_WRITE | REQ_SYNC | REQ_IDLE | REQ_META
>   				  | REQ_PREFLUSH | REQ_FUA,
>   			      GFP_NOIO, &mddev->sync_set);
> +	if (!bio)
> +		return;
>   
>   	atomic_inc(&rdev->nr_pending);
>   
>