| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 65/85] net: unix socket code abuses csum_partial | Date | Thu, 20 Mar 2014 17:10:08 -0700 |
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3.10-stable review patch. If anyone has any objections, please let me know.
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From: Anton Blanchard <anton@samba.org>
commit 0a13404dd3bf4ea870e3d96270b5a382edca85c0 upstream.
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 <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; }
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 <anton@samba.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- net/unix/af_unix.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -160,9 +160,8 @@ static inline void unix_set_secdata(stru 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); }
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