linux-kernel - Re: [PATCH] bnxt: Do not read past the end of test names

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Message-ID: <CACKFLinj6Kn=hsbEWfcPtYjLOZjyMbj1vZG_68r7LrMa7Jf6Rg@mail.gmail.com>
Date:   Wed, 18 Jan 2023 12:59:47 -0800
From:   Michael Chan <michael.chan@...adcom.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Niklas Cassel <Niklas.Cassel@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] bnxt: Do not read past the end of test names

On Wed, Jan 18, 2023 at 12:35 PM Kees Cook <keescook@...omium.org> wrote:
>
> Test names were being concatenated based on a offset beyond the end of
> the first name, which tripped the buffer overflow detection logic:
>
>  detected buffer overflow in strnlen
>  [...]
>  Call Trace:
>  bnxt_ethtool_init.cold+0x18/0x18
>
> Refactor struct hwrm_selftest_qlist_output to use an actual array,
> and adjust the concatenation to use snprintf() rather than a series of
> strncat() calls.
>
> Reported-by: Niklas Cassel <Niklas.Cassel@....com>
> Link: https://lore.kernel.org/lkml/Y8F%2F1w1AZTvLglFX@x1-carbon/
> Tested-by: Niklas Cassel <Niklas.Cassel@....com>
> Fixes: eb51365846bc ("bnxt_en: Add basic ethtool -t selftest support.")
> Cc: Michael Chan <michael.chan@...adcom.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: netdev@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Michael Chan <michael.chan@...adcom.com>

> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_hsi.h b/drivers/net/ethernet/broadcom/bnxt/bnxt_hsi.h
> index 2686a714a59f..a5408879e077 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_hsi.h
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_hsi.h
> @@ -10249,14 +10249,7 @@ struct hwrm_selftest_qlist_output {
>         u8      unused_0;
>         __le16  test_timeout;
>         u8      unused_1[2];
> -       char    test0_name[32];
> -       char    test1_name[32];
> -       char    test2_name[32];
> -       char    test3_name[32];
> -       char    test4_name[32];
> -       char    test5_name[32];
> -       char    test6_name[32];
> -       char    test7_name[32];
> +       char    test_name[8][32];

bnxt_hsi.h is a generated file.  I will need to make a request so that
future versions will be generated like this.

Thanks.

>         u8      eyescope_target_BER_support;
>         #define SELFTEST_QLIST_RESP_EYESCOPE_TARGET_BER_SUPPORT_BER_1E8_SUPPORTED  0x0UL
>         #define SELFTEST_QLIST_RESP_EYESCOPE_TARGET_BER_SUPPORT_BER_1E9_SUPPORTED  0x1UL
> --
> 2.34.1
>

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