Message-ID: <9a2c3c1ef2e879911a1c62a1e8de0ae612727aae.camel@redhat.com>
Subject: Re: [PATCH v2] bnxt: avoid overflow in bnxt_get_nvram_directory()
From:   Paolo Abeni <pabeni@redhat.com>
To:     Simon Horman <simon.horman@corigine.com>,
        Maxim Korotkov <korotkov.maxim.s@gmail.com>
Cc:     Michael Chan <michael.chan@broadcom.com>,
        Pavan Chebbi <pavan.chebbi@broadcom.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org
Date:   Thu, 23 Feb 2023 09:01:20 +0100
In-Reply-To: <5ad788427171d3c0374f24d4714ba0b429cbcfdf.camel@redhat.com>
References: <20230219084656.17926-1-korotkov.maxim.s@gmail.com>
         <Y/Iuu9SiAxh7qhJM@corigine.com>
         <5ad788427171d3c0374f24d4714ba0b429cbcfdf.camel@redhat.com>
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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 da=
ta
> > > type before performing arithmetic. Used macro for multiplication inst=
ead
> > > operator for avoiding overflow.
> > >=20
> > > Found by Security Code and Linux Verification
> > > Center (linuxtesting.org) with SVACE.
> > >=20
> > > Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.")
> > > Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com>
> > > Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
> >=20
> > I agree that it is correct to use mul_u32_u32() for multiplication
> > of two u32 entities where the result is 64bit, avoiding overflow.
> >=20
> > And I agree that the fixes tag indicates the commit where the code
> > in question was introduced.
> >=20
> > 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.
> >=20
> > And thus it is not clear to me if this patch should be for 'net' or
> > 'net-next'.
>=20
> ... 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