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

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Message-ID: <Y8kU10ZFNHJ2Q1IR@x1-carbon>
Date:   Thu, 19 Jan 2023 10:00:55 +0000
From:   Niklas Cassel <Niklas.Cassel@....com>
To:     Kees Cook <keescook@...omium.org>
CC:     Michael Chan <michael.chan@...adcom.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" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hardening@...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 12:35:01PM -0800, Kees Cook 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>
> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c | 13 ++++---------
>  drivers/net/ethernet/broadcom/bnxt/bnxt_hsi.h     |  9 +--------
>  2 files changed, 5 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
> index cbf17fcfb7ab..ec573127b707 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
> @@ -3969,7 +3969,7 @@ void bnxt_ethtool_init(struct bnxt *bp)
>  		test_info->timeout = HWRM_CMD_TIMEOUT;
>  	for (i = 0; i < bp->num_tests; i++) {
>  		char *str = test_info->string[i];
> -		char *fw_str = resp->test0_name + i * 32;
> +		char *fw_str = resp->test_name[i];
>  
>  		if (i == BNXT_MACLPBK_TEST_IDX) {
>  			strcpy(str, "Mac loopback test (offline)");
> @@ -3980,14 +3980,9 @@ void bnxt_ethtool_init(struct bnxt *bp)
>  		} else if (i == BNXT_IRQ_TEST_IDX) {
>  			strcpy(str, "Interrupt_test (offline)");
>  		} else {
> -			strscpy(str, fw_str, ETH_GSTRING_LEN);
> -			strncat(str, " test", ETH_GSTRING_LEN - strlen(str));
> -			if (test_info->offline_mask & (1 << i))
> -				strncat(str, " (offline)",
> -					ETH_GSTRING_LEN - strlen(str));
> -			else
> -				strncat(str, " (online)",
> -					ETH_GSTRING_LEN - strlen(str));
> +			snprintf(str, ETH_GSTRING_LEN, "%s test (%s)",
> +				 fw_str, test_info->offline_mask & (1 << i) ?
> +					"offline" : "online");
>  		}
>  	}
>  
> 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];
>  	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
> 

Reviewed-by: Niklas Cassel <niklas.cassel@....com>