[PATCH 6.1 102/127] fs/sysv: Null check to prevent null-ptr-deref bug

Greg Kroah-Hartman
2023-08-09T10:57:10Z

From: Prince Kumar Maurya <princekumarmaurya06@gmail.com>

commit ea2b62f305893992156a798f665847e0663c9f41 upstream.

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

Reported-by: syzbot+aad58150cbc64ba41bdc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=aad58150cbc64ba41bdc
Signed-off-by: Prince Kumar Maurya <princekumarmaurya06@gmail.com>
Message-Id: <20230531013141.19487-1-princekumarmaurya06@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/sysv/itree.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/fs/sysv/itree.c
+++ b/fs/sysv/itree.c
@@ -145,6 +145,10 @@ static int alloc_branch(struct inode *in
*/
parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
bh = sb_getblk(inode->i_sb, parent);
+ if (!bh) {
+ sysv_free_block(inode->i_sb, branch[n].key);
+ break;
+ }
lock_buffer(bh);
memset(bh->b_data, 0, blocksize);
branch[n].bh = bh;