Re: [PATCH] fs/ntfs3: Fix slab-out-of-bounds read in hdr_delete_de()

[Konstantin Komarov <almaz.alexandrovich@paragon-software.com>]

On 12.12.2022 05:31, Zeng Heng wrote:
> Here is a BUG report from syzbot:
>
> BUG: KASAN: slab-out-of-bounds in hdr_delete_de+0xe0/0x150 fs/ntfs3/index.c:806
> Read of size 16842960 at addr ffff888079cc0600 by task syz-executor934/3631
>
> Call Trace:
>   memmove+0x25/0x60 mm/kasan/shadow.c:54
>   hdr_delete_de+0xe0/0x150 fs/ntfs3/index.c:806
>   indx_delete_entry+0x74f/0x3670 fs/ntfs3/index.c:2193
>   ni_remove_name+0x27a/0x980 fs/ntfs3/frecord.c:2910
>   ntfs_unlink_inode+0x3d4/0x720 fs/ntfs3/inode.c:1712
>   ntfs_rename+0x41a/0xcb0 fs/ntfs3/namei.c:276
>
> Before using the meta-data in struct INDEX_HDR, we need to
> check index header valid or not. Otherwise, the corruptedi
> (or malicious) fs image can cause out-of-bounds access which
> could make kernel panic.
>
> Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
> Reported-by: syzbot+9c2811fd56591639ff5f@syzkaller.appspotmail.com
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> ---
>   fs/ntfs3/fslog.c   | 2 +-
>   fs/ntfs3/index.c   | 4 ++++
>   fs/ntfs3/ntfs_fs.h | 1 +
>   3 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ntfs3/fslog.c b/fs/ntfs3/fslog.c
> index 0d611a6c5511..0de2bbb42721 100644
> --- a/fs/ntfs3/fslog.c
> +++ b/fs/ntfs3/fslog.c
> @@ -2597,7 +2597,7 @@ static int read_next_log_rec(struct ntfs_log *log, struct lcb *lcb, u64 *lsn)
>   	return find_log_rec(log, *lsn, lcb);
>   }
>   
> -static inline bool check_index_header(const struct INDEX_HDR *hdr, size_t bytes)
> +bool check_index_header(const struct INDEX_HDR *hdr, size_t bytes)
>   {
>   	__le16 mask;
>   	u32 min_de, de_off, used, total;
> diff --git a/fs/ntfs3/index.c b/fs/ntfs3/index.c
> index 440328147e7e..6f5d8dd6659d 100644
> --- a/fs/ntfs3/index.c
> +++ b/fs/ntfs3/index.c
> @@ -798,6 +798,10 @@ static inline struct NTFS_DE *hdr_delete_de(struct INDEX_HDR *hdr,
>   	u32 off = PtrOffset(hdr, re);
>   	int bytes = used - (off + esize);
>   
> +	/* check INDEX_HDR valid before using INDEX_HDR */
> +	if (!check_index_header(hdr, le32_to_cpu(hdr->total)))
> +		return NULL;
> +
>   	if (off >= used || esize < sizeof(struct NTFS_DE) ||
>   	    bytes < sizeof(struct NTFS_DE))
>   		return NULL;
> diff --git a/fs/ntfs3/ntfs_fs.h b/fs/ntfs3/ntfs_fs.h
> index 2c791222c4e2..c5c022fef4e0 100644
> --- a/fs/ntfs3/ntfs_fs.h
> +++ b/fs/ntfs3/ntfs_fs.h
> @@ -574,6 +574,7 @@ int ni_rename(struct ntfs_inode *dir_ni, struct ntfs_inode *new_dir_ni,
>   bool ni_is_dirty(struct inode *inode);
>   
>   /* Globals from fslog.c */
> +bool check_index_header(const struct INDEX_HDR *hdr, size_t bytes);
>   int log_replay(struct ntfs_inode *ni, bool *initialized);
>   
>   /* Globals from fsntfs.c */
Thanks for patch, applied!