2022-10-30 07:33:44

by Abdun Nihaal

Subject: [PATCH] fs/ntfs3: Fix NULL dereference in ni_write_inode

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: [email protected]
Signed-off-by: Abdun Nihaal <[email protected]>
---
fs/ntfs3/frecord.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
index 70a80f9412f7..e55bbd209ef8 100644
--- a/fs/ntfs3/frecord.c
+++ b/fs/ntfs3/frecord.c
@@ -3243,6 +3243,9 @@ 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;
--
2.37.3

2022-12-30 07:42:42

by Konstantin Komarov

Subject: Re: [PATCH] fs/ntfs3: Fix NULL dereference in ni_write_inode

On 30.10.2022 11:02, Abdun Nihaal wrote:
> 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: [email protected]
> Signed-off-by: Abdun Nihaal <[email protected]>
> ---
> fs/ntfs3/frecord.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
> index 70a80f9412f7..e55bbd209ef8 100644
> --- a/fs/ntfs3/frecord.c
> +++ b/fs/ntfs3/frecord.c
> @@ -3243,6 +3243,9 @@ 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;
Thank you for your work, applied!