linux-kernel - Re: [PATCH v4] ntfs : fix shift-out-of-bounds in ntfs

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Message-ID: <CAKYAXd8A9+Zcg=8wLV0h4fdcvybp=BB-a0yRKSTHmk0sQi26_A@mail.gmail.com>
Date:   Mon, 14 Aug 2023 10:02:24 +0900
From:   Namjae Jeon <linkinjeon@...nel.org>
To:     Manas Ghandat <ghandatmanas@...il.com>, anton@...era.com
Cc:     gregkh@...uxfoundation.org,
        Linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ntfs-dev@...ts.sourceforge.net,
        syzbot+4768a8f039aa677897d0@...kaller.appspotmail.com
Subject: Re: [PATCH v4] ntfs : fix shift-out-of-bounds in ntfs_iget

2023-08-13 14:59 GMT+09:00, Manas Ghandat <ghandatmanas@...il.com>:
Hi,
> Currently there is not check for ni->itype.compressed.block_size when
> a->data.non_resident.compression_unit is present and NInoSparse(ni) is
> true. Added the required check to calculation of block size.
>
> Signed-off-by: Manas Ghandat <ghandatmanas@...il.com>
> Reported-by: syzbot+4768a8f039aa677897d0@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=4768a8f039aa677897d0
> Fix-commit-ID: upstream f40ddce88593482919761f74910f42f4b84c004b
> ---
> V3 -> V4: Fix description
> V2 -> V3: Fix patching issue.
> V1 -> V2: Cleaned up coding style.
>
>  fs/ntfs/inode.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
> index 6c3f38d66579..a657322874ed 100644
> --- a/fs/ntfs/inode.c
> +++ b/fs/ntfs/inode.c
> @@ -1077,6 +1077,15 @@ static int ntfs_read_locked_inode(struct inode *vi)
>  					goto unm_err_out;
>  				}
>  				if (a->data.non_resident.compression_unit) {
> +					if (a->data.non_resident.compression_unit +
> +					vol->cluster_size_bits > 32) {
> +						ntfs_error(vi->i_sb,
> +						"Found non-standard compression unit (%u).   Cannot handle this.",
> +						a->data.non_resident.compression_unit
> +						);
> +						err = -EOPNOTSUPP;
> +						goto unm_err_out;
> +					}
compression_unit seems to be used when the ntfs inode is compressed.
And it should be either 0 or 4 value. So, I think we can set related
compression block variables of ntfs inode only when ni is
NInoCompressed like this... Anton, Am I missing something ?

diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index efe0602b4e51..e5a7d81d575b 100644
--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -1076,7 +1076,8 @@ static int ntfs_read_locked_inode(struct inode *vi)
                                        err = -EOPNOTSUPP;
                                        goto unm_err_out;
                                }
-                               if (a->data.non_resident.compression_unit) {
+                               if (NInoCompressed(ni) &&
+                                   a->data.non_resident.compression_unit) {
                                        ni->itype.compressed.block_size = 1U <<
                                                        (a->data.non_resident.
                                                        compression_unit +

>  					ni->itype.compressed.block_size = 1U <<
>  							(a->data.non_resident.
>  							compression_unit +
> --
> 2.37.2
>
>