[PATCH 5.15 008/124] etherdevice: Adjust ether_addr* prototypes to silence -Wstringop-overead

From: Greg Kroah-Hartman
Date: Tue Apr 26 2022 - 05:13:40 EST

From: Kees Cook <keescook@xxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
Tested-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/netdev/20220212090811.uuzk6d76agw2vv73@xxxxxxxxxxxxxx
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Khem Raj <raj.khem@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
include/linux/etherdevice.h | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -127,7 +127,7 @@ static inline bool is_multicast_ether_ad

-static inline bool is_multicast_ether_addr_64bits(const u8 addr[6+2])
+static inline bool is_multicast_ether_addr_64bits(const u8 *addr)
#ifdef __BIG_ENDIAN
@@ -364,8 +364,7 @@ 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)
u64 fold = (*(const u64 *)addr1) ^ (*(const u64 *)addr2);