netdev - [PATCH] bnxt_en: avoid string overflow for record->system

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Date:   Mon, 13 Aug 2018 23:26:54 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Michael Chan <michael.chan@...adcom.com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Vasundhara Volam <vasundhara-v.volam@...adcom.com>,
        Scott Branden <scott.branden@...adcom.com>,
        Andy Gospodarek <gospo@...adcom.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] bnxt_en: avoid string overflow for record->system_name

The utsname()->nodename string may be 64 bytes long, and it gets
copied without the trailing nul byte into the shorter record->system_name,
as gcc now warns:

In file included from include/linux/bitmap.h:9,
                 from include/linux/ethtool.h:16,
                 from drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c:13:
In function 'strncpy',
    inlined from 'bnxt_fill_coredump_record' at drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c:2863:2:
include/linux/string.h:254:9: error: '__builtin_strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Werror=stringop-truncation]

Using strlcpy() at least avoids overflowing the destination buffer
and adds proper nul-termination. It may still truncate long names
though, which probably can't be solved here.

Fixes: 6c5657d085ae ("bnxt_en: Add support for ethtool get dump.")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
index b1602ea64372..e52d7af3ab3e 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
@@ -2860,8 +2860,8 @@ bnxt_fill_coredump_record(struct bnxt *bp, struct bnxt_coredump_record *record,
 	record->low_version = 0;
 	record->high_version = 1;
 	record->asic_state = 0;
-	strncpy(record->system_name, utsname()->nodename,
-		strlen(utsname()->nodename));
+	strlcpy(record->system_name, utsname()->nodename,
+		sizeof(record->system_name));
 	record->year = cpu_to_le16(tm.tm_year);
 	record->month = cpu_to_le16(tm.tm_mon);
 	record->day = cpu_to_le16(tm.tm_mday);
-- 
2.18.0