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From:   Anton Altaparmakov <anton@tuxera.com>
To:     Andrew Morton <akpm@linux-foundation.org>
CC:     "linux-ntfs-dev@lists.sourceforge.net" 
        <linux-ntfs-dev@lists.sourceforge.net>,
        LKML <linux-kernel@vger.kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Rustam Kovhaev <rkovhaev@gmail.com>
Subject: Re: [PATCH] ntfs: add check for mft record size in superblock
Thread-Topic: [PATCH] ntfs: add check for mft record size in superblock
Thread-Index: AQHWeb4qTTgnzi6Afk6ibcYrpfnrp6lGW56A
Date:   Mon, 24 Aug 2020 02:46:00 +0000
Message-ID: <E72182A7-D6F9-4AE3-95B3-B732B2F0D7BD@tuxera.com>
References: <20200824022804.226242-1-rkovhaev@gmail.com>
In-Reply-To: <20200824022804.226242-1-rkovhaev@gmail.com>
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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@gmail.com> 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@syzkaller.appspotmail.com
> Link: https://syzkaller.appspot.com/bug?extid=aed06913f36eff9b544e
> Signed-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
> Acked-by: Anton Altaparmakov <anton@tuxera.com>
> ---
> 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