SUNRPC: Fix error return value of svc_addr_len()

The svc_addr_len() helper function returns -EAFNOSUPPORT if it doesn't
recognize the address family of the passed-in socket address.  However,
the return type of this function is size_t, which means -EAFNOSUPPORT
is turned into a very large positive value in this case.

The check in svc_udp_recvfrom() to see if the return value is less
than zero therefore won't work at all.

Additionally, handle_connect_req() passes this value directly to
memset().  This could cause memset() to clobber a large chunk of memory
if svc_addr_len() has returned an error.  Currently the address family
of these addresses, however, is known to be supported long before
handle_connect_req() is called, so this isn't a real risk.

Change the error return value of svc_addr_len() to zero, which fits in
the range of size_t, and is safer to pass to memset() directly.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

2 files changed, 7 insertions, 5 deletions

diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h
index 0d9cb6ef28b0..d790c52525cc 100644
--- a/include/linux/sunrpc/svc_xprt.h
+++ b/include/linux/sunrpc/svc_xprt.h
@@ -118,7 +118,7 @@ static inline unsigned short svc_addr_port(const struct sockaddr *sa)
         return 0;
 }
 
-static inline size_t svc_addr_len(struct sockaddr *sa)
+static inline size_t svc_addr_len(const struct sockaddr *sa)
 {
         switch (sa->sa_family) {
         case AF_INET:
@@ -126,7 +126,8 @@ static inline size_t svc_addr_len(struct sockaddr *sa)
         case AF_INET6:
                 return sizeof(struct sockaddr_in6);
         }
-        return -EAFNOSUPPORT;
+
+        return 0;
 }
 
 static inline unsigned short svc_xprt_local_port(const struct svc_xprt *xprt)
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index af3198814c15..8b0832834135 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -426,13 +426,14 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
                 long            all[SVC_PKTINFO_SPACE / sizeof(long)];
         } buffer;
         struct cmsghdr *cmh = &buffer.hdr;
-        int             err, len;
         struct msghdr msg = {
                 .msg_name = svc_addr(rqstp),
                 .msg_control = cmh,
                 .msg_controllen = sizeof(buffer),
                 .msg_flags = MSG_DONTWAIT,
         };
+        size_t len;
+        int err;
 
         if (test_and_clear_bit(XPT_CHNGBUF, &svsk->sk_xprt.xpt_flags))
             /* udp sockets need large rcvbuf as all pending
@@ -464,8 +465,8 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
                 return -EAGAIN;
         }
         len = svc_addr_len(svc_addr(rqstp));
-        if (len < 0)
-                return len;
+        if (len == 0)
+                return -EAFNOSUPPORT;
         rqstp->rq_addrlen = len;
         if (skb->tstamp.tv64 == 0) {
                 skb->tstamp = ktime_get_real();