Re: [PATCH 1/2] Revert "UBIFS: Fix potential integer overflow in allocation"

[Kees Cook]

On Sun, Jul 1, 2018 at 2:20 PM, Richard Weinberger <richard@xxxxxx> wrote:
> This reverts commit 353748a359f1821ee934afc579cf04572406b420.
> It bypassed the linux-mtd review process and fixes the issue not as it
> should.

Ah, sorry, I thought you were CCed on the original report.

> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Silvio Cesare <silvio.cesare@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Richard Weinberger <richard@xxxxxx>
> ---
>  fs/ubifs/journal.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
> index 07b4956e0425..da8afdfccaa6 100644
> --- a/fs/ubifs/journal.c
> +++ b/fs/ubifs/journal.c
> @@ -1282,11 +1282,10 @@ static int truncate_data_node(const struct ubifs_info *c, const struct inode *in
>                               int *new_len)
>  {
>         void *buf;
> -       int err, compr_type;
> -       u32 dlen, out_len, old_dlen;
> +       int err, dlen, compr_type, out_len, old_dlen;

What's wrong with making these unsigned?

>
>         out_len = le32_to_cpu(dn->size);
> -       buf = kmalloc_array(out_len, WORST_COMPR_FACTOR, GFP_NOFS);
> +       buf = kmalloc(out_len * WORST_COMPR_FACTOR, GFP_NOFS);
>         if (!buf)
>                 return -ENOMEM;

Please leave the kmalloc() -> kmalloc_array() change, as that has
happened treewide already. We don't want to have any multiplications
in the size argument for the allocators (i.e. they should use 2-factor
arg version like here, or use array_size() for things like vmalloc()).

Thanks!

-Kees

-- 
Kees Cook
Pixel Security