From: Johannes Berg Date: Mon, 7 May 2012 13:39:06 +0000 (+0200) Subject: net: compare_ether_addr[_64bits]() has no ordering X-Git-Tag: Ubuntu-5.0.0-8.9~16138^2~14 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=1c430a727fa512500a422ffe4712166c550ea06a;p=mirror_ubuntu-disco-kernel.git net: compare_ether_addr[_64bits]() has no ordering Neither compare_ether_addr() nor compare_ether_addr_64bits() (as it can fall back to the former) have comparison semantics like memcmp() where the sign of the return value indicates sort order. We had a bug in the wireless code due to a blind memcmp replacement because of this. A cursory look suggests that the wireless bug was the only one due to this semantic difference. Signed-off-by: Johannes Berg Signed-off-by: David S. Miller --- diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h index 8a1835855faa..fe5136d81454 100644 --- a/include/linux/etherdevice.h +++ b/include/linux/etherdevice.h @@ -159,7 +159,8 @@ static inline void eth_hw_addr_random(struct net_device *dev) * @addr1: Pointer to a six-byte array containing the Ethernet address * @addr2: Pointer other six-byte array containing the Ethernet address * - * Compare two ethernet addresses, returns 0 if equal + * Compare two ethernet addresses, returns 0 if equal, non-zero otherwise. + * Unlike memcmp(), it doesn't return a value suitable for sorting. */ static inline unsigned compare_ether_addr(const u8 *addr1, const u8 *addr2) { @@ -184,10 +185,10 @@ static inline unsigned long zap_last_2bytes(unsigned long value) * @addr1: Pointer to an array of 8 bytes * @addr2: Pointer to an other array of 8 bytes * - * Compare two ethernet addresses, returns 0 if equal. - * Same result than "memcmp(addr1, addr2, ETH_ALEN)" but without conditional - * branches, and possibly long word memory accesses on CPU allowing cheap - * unaligned memory reads. + * Compare two ethernet addresses, returns 0 if equal, non-zero otherwise. + * Unlike memcmp(), it doesn't return a value suitable for sorting. + * The function doesn't need any conditional branches and possibly uses + * word memory accesses on CPU allowing cheap unaligned memory reads. * arrays = { byte1, byte2, byte3, byte4, byte6, byte7, pad1, pad2} * * Please note that alignment of addr1 & addr2 is only guaranted to be 16 bits.