Re: [PATCH] ntfs: add check for mft record size in superblock

[Anton Altaparmakov]

Hi Andrew,

Can you please merge this patch?  Thanks a lot in advance!

Rustam, thank you for the updated patch!

Best regards,

	Anton

> On 24 Aug 2020, at 03:28, Rustam Kovhaev <rkovhaev@xxxxxxxxx> wrote:
> 
> number of bytes allocated for mft record should be equal to the mft
> record size stored in ntfs superblock
> as reported by syzbot, userspace might trigger out-of-bounds read by
> dereferencing ctx->attr in ntfs_attr_find()
> 
> Reported-and-tested-by: syzbot+aed06913f36eff9b544e@xxxxxxxxxxxxxxxxxxxxxxxxx
> Link: https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e
> Signed-off-by: Rustam Kovhaev <rkovhaev@xxxxxxxxx>
> Acked-by: Anton Altaparmakov <anton@xxxxxxxxxx>
> ---
> fs/ntfs/inode.c | 6 ++++++
> 1 file changed, 6 insertions(+)
> 
> diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
> index 9bb9f0952b18..caf563981532 100644
> --- a/fs/ntfs/inode.c
> +++ b/fs/ntfs/inode.c
> @@ -1810,6 +1810,12 @@ int ntfs_read_inode_mount(struct inode *vi)
> 		brelse(bh);
> 	}
> 
> +	if (le32_to_cpu(m->bytes_allocated) != vol->mft_record_size) {
> +		ntfs_error(sb, "Incorrect mft record size %u in superblock, should be %u.",
> +				le32_to_cpu(m->bytes_allocated), vol->mft_record_size);
> +		goto err_out;
> +	}
> +
> 	/* Apply the mst fixups. */
> 	if (post_read_mst_fixup((NTFS_RECORD*)m, vol->mft_record_size)) {
> 		/* FIXME: Try to use the $MFTMirr now. */
> -- 
> 2.28.0
> 


-- 
Anton Altaparmakov <anton at tuxera.com> (replace at with @)
Lead in File System Development, Tuxera Inc., http://www.tuxera.com/
Linux NTFS maintainer