linux-kernel - [PATCH 4.9 01/24] etherdevice: Adjust ether_addr* prototypes to silence -Wstringop-overead

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Message-Id: <20220426081731.416160676@linuxfoundation.org>
Date:   Tue, 26 Apr 2022 10:20:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marc Kleine-Budde <mkl@...gutronix.de>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        Khem Raj <raj.khem@...il.com>
Subject: [PATCH 4.9 01/24] etherdevice: Adjust ether_addr* prototypes to silence -Wstringop-overead

From: Kees Cook <keescook@...omium.org>

commit 2618a0dae09ef37728dab89ff60418cbe25ae6bd upstream.

With GCC 12, -Wstringop-overread was warning about an implicit cast from
char[6] to char[8]. However, the extra 2 bytes are always thrown away,
alignment doesn't matter, and the risk of hitting the edge of unallocated
memory has been accepted, so this prototype can just be converted to a
regular char *. Silences:

net/core/dev.c: In function ‘bpf_prog_run_generic_xdp’: net/core/dev.c:4618:21: warning: ‘ether_addr_equal_64bits’ reading 8 bytes from a region of size 6 [-Wstringop-overread]
 4618 |         orig_host = ether_addr_equal_64bits(eth->h_dest, > skb->dev->dev_addr);
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/core/dev.c:4618:21: note: referencing argument 1 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
net/core/dev.c:4618:21: note: referencing argument 2 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
In file included from net/core/dev.c:91: include/linux/etherdevice.h:375:20: note: in a call to function ‘ether_addr_equal_64bits’
  375 | static inline bool ether_addr_equal_64bits(const u8 addr1[6+2],
      |                    ^~~~~~~~~~~~~~~~~~~~~~~

Reported-by: Marc Kleine-Budde <mkl@...gutronix.de>
Tested-by: Marc Kleine-Budde <mkl@...gutronix.de>
Link: https://lore.kernel.org/netdev/20220212090811.uuzk6d76agw2vv73@pengutronix.de
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Cc: Khem Raj <raj.khem@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/linux/etherdevice.h |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -125,7 +125,7 @@ static inline bool is_multicast_ether_ad
 #endif
 }
 
-static inline bool is_multicast_ether_addr_64bits(const u8 addr[6+2])
+static inline bool is_multicast_ether_addr_64bits(const u8 *addr)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
 #ifdef __BIG_ENDIAN
@@ -339,8 +339,7 @@ static inline bool ether_addr_equal(cons
  * Please note that alignment of addr1 & addr2 are only guaranteed to be 16 bits.
  */
 
-static inline bool ether_addr_equal_64bits(const u8 addr1[6+2],
-					   const u8 addr2[6+2])
+static inline bool ether_addr_equal_64bits(const u8 *addr1, const u8 *addr2)
 {
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && BITS_PER_LONG == 64
 	u64 fold = (*(const u64 *)addr1) ^ (*(const u64 *)addr2);