Re: [PATCH 2/2] ubifs: Check data node size before truncate

[Kees Cook]

On Sun, Jul 1, 2018 at 2:20 PM, Richard Weinberger <richard@xxxxxx> wrote:
> Check whether the size is within bounds before using it.
> If the size is not correct, abort and dump the bad data node.
>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Silvio Cesare <silvio.cesare@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 1e51764a3c2ac ("UBIFS: add new flash file system")
> Reported-by: Silvio Cesare <silvio.cesare@xxxxxxxxx>
> Signed-off-by: Richard Weinberger <richard@xxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> ---
>  fs/ubifs/journal.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
> index da8afdfccaa6..eea12d25a58b 100644
> --- a/fs/ubifs/journal.c
> +++ b/fs/ubifs/journal.c
> @@ -1387,7 +1387,16 @@ int ubifs_jnl_truncate(struct ubifs_info *c, const struct inode *inode,
>                 else if (err)
>                         goto out_free;
>                 else {
> -                       if (le32_to_cpu(dn->size) <= dlen)
> +                       int dn_len = le32_to_cpu(dn->size);
> +
> +                       if (dn_len <= 0 || dn_len > UBIFS_BLOCK_SIZE) {
> +                               ubifs_err(c, "bad data node (block %u, inode %lu)",
> +                                         blk, inode->i_ino);
> +                               ubifs_dump_node(c, dn);
> +                               goto out_free;
> +                       }
> +
> +                       if (dn_len <= dlen)
>                                 dlen = 0; /* Nothing to do */
>                         else {
>                                 err = truncate_data_node(c, inode, blk, dn, &dlen);
> --
> 2.18.0
>



-- 
Kees Cook
Pixel Security