Re: [PATCH v2] bnxt: avoid overflow in bnxt_get_nvram_directory()

[Maxim Korotkov]

23.02.2023 11:01, Paolo Abeni wrote:
> On Tue, 2023-02-21 at 10:34 +0100, Paolo Abeni wrote:
> > On Sun, 2023-02-19 at 15:14 +0100, Simon Horman wrote:
> > > On Sun, Feb 19, 2023 at 11:46:56AM +0300, Maxim Korotkov wrote:
> > > > The value of an arithmetic expression is subject
> > > > of possible overflow due to a failure to cast operands to a larger data
> > > > type before performing arithmetic. Used macro for multiplication instead
> > > > operator for avoiding overflow.
> > > >
> > > > Found by Security Code and Linux Verification
> > > > Center (linuxtesting.org) with SVACE.
> > > >
> > > > Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.")
> > > > Signed-off-by: Maxim Korotkov <korotkov.maxim.s@xxxxxxxxx>
> > > > Reviewed-by: Pavan Chebbi <pavan.chebbi@xxxxxxxxxxxx>
> > >
> > > I agree that it is correct to use mul_u32_u32() for multiplication
> > > of two u32 entities where the result is 64bit, avoiding overflow.
> > >
> > > And I agree that the fixes tag indicates the commit where the code
> > > in question was introduced.
> > >
> > > However, it is not clear to me if this is a theoretical bug
> > > or one that can manifest in practice - I think it implies that
> > > buflen really can be > 4Gbytes.
> > >
> > > And thus it is not clear to me if this patch should be for 'net' or
> > > 'net-next'.
> >
> > ... especially considered that both 'dir_entries' and 'entry_length'
> > are copied back to the user-space using a single byte each.
>
> To be clear: if this is really a bug you should update the commit
> message stating how the bug could happen. Otherwise you could repost
> for net-next stripping the fixes tag.
>
> Thanks,
>
> Paolo
This is more of a hypothetical issue in my opinion. At least I don't 
have proof of concept. I'll resend this patch when net-next tree be open.
Best regards, Max