Re: [PATCH] btrfs: backref: this patch fixes a null pointer dereference bug.

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

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On 2020/8/6 下午2:31, Boleyn Su wrote:
> The `if (!ret)` check will always be false and it may result in ret->path
> being dereferenced while it is a null pointer.
> 
> Fixes: a37f232b7b65 ("btrfs: backref: introduce the skeleton of btrfs_backref_iter")
> Cc: Chris Mason <clm@fb.com>
> Cc: Josef Bacik <josef@toxicpanda.com>
> Cc: David Sterba <dsterba@suse.com>
> Cc: Boleyn Su <boleyn.su@gmail.com>
> Cc: linux-btrfs@vger.kernel.org
> Signed-off-by: Boleyn Su <boleynsu@google.com>

Nice catch.

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu
> ---
>  fs/btrfs/backref.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
> index ea10f7bc9..ea1c28ccb 100644
> --- a/fs/btrfs/backref.c
> +++ b/fs/btrfs/backref.c
> @@ -2303,7 +2303,7 @@ struct btrfs_backref_iter *btrfs_backref_iter_alloc(
>  		return NULL;
>  
>  	ret->path = btrfs_alloc_path();
> -	if (!ret) {
> +	if (!ret->path) {
>  		kfree(ret);
>  		return NULL;
>  	}
> 


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