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author | Anton Blanchard <anton@samba.org> | 2014-03-05 14:29:58 +1100 |
---|---|---|
committer | Ben Hutchings <ben@decadent.org.uk> | 2014-04-02 00:58:58 +0100 |
commit | 426a3d1bf77735722ef23691fcc7cc14c3264aef (patch) | |
tree | 9fb1555fb189ff929cde47e1ca39de8142bcc15c | |
parent | 8197077f9fc59c76180360af754741776cc803b1 (diff) | |
download | lwn-426a3d1bf77735722ef23691fcc7cc14c3264aef.tar.gz lwn-426a3d1bf77735722ef23691fcc7cc14c3264aef.zip |
net: unix socket code abuses csum_partial
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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r-- | net/unix/af_unix.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index eddfdecc122b..54fc90b2408e 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -149,8 +149,8 @@ static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb) static inline unsigned unix_hash_fold(__wsum n) { - unsigned hash = (__force unsigned)n; - hash ^= hash>>16; + unsigned int hash = (__force unsigned int)csum_fold(n); + hash ^= hash>>8; return hash&(UNIX_HASH_SIZE-1); } |