The unix socket code is using the result of csum_partial to hash into a lookup table: unix_hash_fold(csum_partial(sunaddr, len, 0)); csum_partial is only guaranteed to produce something that can be folded into a checksum, as its prototype explains: * returns a 32-bit number suitable for feeding into itself * or csum_tcpudp_magic The 32bit value should not be used directly. Depending on the alignment the ppc64 csum_partial will return different 32bit values that will fold into the same checksum. This difference causes the following testcase (courtesy of Gustavo) to sometimes fail: #include <sys/socket.h> #include <stdio.h> int main() { int fd = socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0); int i = 1; setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &i, 4); struct sockaddr addr; addr.sa_family = AF_LOCAL; bind(fd, &addr, 2); listen(fd, 128); struct sockaddr_storage ss; socklen_t sslen = (socklen_t)sizeof(ss); getsockname(fd, (struct sockaddr*)&ss, &sslen); fd = socket(PF_LOCAL, SOCK_STREAM|SOCK_CLOEXEC, 0); if (connect(fd, (struct sockaddr*)&ss, sslen) == -1){ perror(NULL); return 1; } printf("OK\n"); return 0; } Use jhash instead of the current hand crafted csum_partial + xor based hash. Signed-off-by: Anton Blanchard <anton@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- Would appreciate a sanity check here. Are there other users that expect a stable 32bit value out of csum_partial? Is this performance critical enough that jhash is going to hurt? Another option would be to csum_fold the 32bit intermediate value and just hash based on the result. Index: b/net/unix/af_unix.c =================================================================== --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -117,6 +117,7 @@ #include <net/checksum.h> #include <linux/security.h> #include <linux/freezer.h> +#include <linux/jhash.h> struct hlist_head unix_socket_table[2 * UNIX_HASH_SIZE]; EXPORT_SYMBOL_GPL(unix_socket_table); @@ -161,13 +162,9 @@ static inline void unix_set_secdata(stru * each socket state is protected by separate spin lock. */ -static inline unsigned int unix_hash_fold(__wsum n) +static inline unsigned int unix_hash(void *data, unsigned int len) { - unsigned int hash = (__force unsigned int)n; - - hash ^= hash>>16; - hash ^= hash>>8; - return hash&(UNIX_HASH_SIZE-1); + return jhash(data, len, 0) & (UNIX_HASH_SIZE - 1); } #define unix_peer(sk) (unix_sk(sk)->peer) @@ -232,7 +229,7 @@ static int unix_mkname(struct sockaddr_u return len; } - *hashp = unix_hash_fold(csum_partial(sunaddr, len, 0)); + *hashp = unix_hash(sunaddr, len); return len; } @@ -738,7 +735,7 @@ static int unix_autobind(struct socket * retry: addr->len = sprintf(addr->name->sun_path+1, "%05x", ordernum) + 1 + sizeof(short); - addr->hash = unix_hash_fold(csum_partial(addr->name, addr->len, 0)); + addr->hash = unix_hash(addr->name, addr->len); spin_lock(&unix_table_lock); ordernum = (ordernum+1)&0xFFFFF; -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html