[PATCH AUTOSEL 6.2 06/18] fs/ntfs3: Fix NULL dereference in ni_write_inode

[Sasha Levin]

From: Abdun Nihaal <abdun.nihaal@xxxxxxxxx>

[ Upstream commit 8dae4f6341e335a09575be60b4fdf697c732a470 ]

Syzbot reports a NULL dereference in ni_write_inode.
When creating a new inode, if allocation fails in mi_init function
(called in mi_format_new function), mi->mrec is set to NULL.
In the error path of this inode creation, mi->mrec is later
dereferenced in ni_write_inode.

Add a NULL check to prevent NULL dereference.

Link: https://syzkaller.appspot.com/bug?extid=f45957555ed4a808cc7a
Reported-and-tested-by: syzbot+f45957555ed4a808cc7a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Abdun Nihaal <abdun.nihaal@xxxxxxxxx>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/ntfs3/frecord.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
index f1df52dfab74b..912eeb3d34717 100644
--- a/fs/ntfs3/frecord.c
+++ b/fs/ntfs3/frecord.c
@@ -3258,6 +3258,9 @@ int ni_write_inode(struct inode *inode, int sync, const char *hint)
 		return 0;
 	}
 
+	if (!ni->mi.mrec)
+		goto out;
+
 	if (is_rec_inuse(ni->mi.mrec) &&
 	    !(sbi->flags & NTFS_FLAGS_LOG_REPLAYING) && inode->i_nlink) {
 		bool modified = false;
-- 
2.39.2