[v1] Null check to prevent null-ptr-deref bug

[PATCH] Null check to prevent null-ptr-deref bug

Posted by Prince Kumar Maurya 2 years, 8 months ago

sb_getblk(inode->i_sb, parent) return a null ptr and taking lock on that leads to the null-ptr-deref bug.

Signed-off-by: Prince Kumar Maurya <princekumarmaurya06@gmail.com>
---
 fs/sysv/itree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/sysv/itree.c b/fs/sysv/itree.c
index b22764fe669c..3a6b66e719fd 100644
--- a/fs/sysv/itree.c
+++ b/fs/sysv/itree.c
@@ -145,6 +145,8 @@ static int alloc_branch(struct inode *inode,
 		 */
 		parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
 		bh = sb_getblk(inode->i_sb, parent);
+		if (!bh)
+			break;
 		lock_buffer(bh);
 		memset(bh->b_data, 0, blocksize);
 		branch[n].bh = bh;
-- 
2.40.1

Re: [PATCH] Null check to prevent null-ptr-deref bug

Posted by Greg KH 2 years, 8 months ago

On Sun, May 28, 2023 at 09:44:00AM -0700, Prince Kumar Maurya wrote:
> sb_getblk(inode->i_sb, parent) return a null ptr and taking lock on that leads to the null-ptr-deref bug.
> 
> Signed-off-by: Prince Kumar Maurya <princekumarmaurya06@gmail.com>
> ---
>  fs/sysv/itree.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/sysv/itree.c b/fs/sysv/itree.c
> index b22764fe669c..3a6b66e719fd 100644
> --- a/fs/sysv/itree.c
> +++ b/fs/sysv/itree.c
> @@ -145,6 +145,8 @@ static int alloc_branch(struct inode *inode,
>  		 */
>  		parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
>  		bh = sb_getblk(inode->i_sb, parent);
> +		if (!bh)
> +			break;
>  		lock_buffer(bh);
>  		memset(bh->b_data, 0, blocksize);
>  		branch[n].bh = bh;
> -- 
> 2.40.1

Why resend this when I already responded:
	https://lore.kernel.org/r/2023052803-pucker-depress-5452@gregkh

confused,

greg k-h