From 0a13404dd3bf4ea870e3d96270b5a382edca85c0 Mon Sep 17 00:00:00 2001 From: Anton Blanchard Date: Wed, 5 Mar 2014 14:29:58 +1100 Subject: net: unix socket code abuses csum_partial 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 partial checksums that will fold into the same 16bit checksum. This difference causes the following testcase (courtesy of Gustavo) to sometimes fail: #include #include 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; } As suggested by davem, fix this by using csum_fold to fold the partial 32bit checksum into a 16bit checksum before using it. Signed-off-by: Anton Blanchard Cc: stable@vger.kernel.org Signed-off-by: David S. Miller --- net/unix/af_unix.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'net/unix') diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 29fc8bee9702..ce6ec6c2f4de 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -163,9 +163,8 @@ static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb) static inline unsigned int unix_hash_fold(__wsum n) { - unsigned int hash = (__force unsigned int)n; + unsigned int hash = (__force unsigned int)csum_fold(n); - hash ^= hash>>16; hash ^= hash>>8; return hash&(UNIX_HASH_SIZE-1); } -- cgit v1.2.3