[PATCH] knfsd: Fix some minor sign problems in nfsd/xdr

There are a couple of tests which could possibly be confused by extremely
large numbers appearing in 'xdr' packets.  I think the closest to an exploit
you could get would be writing random data from a free page into a file - i.e.
 leak data out of kernel space.

I'm fairly sure they cannot be used for remote compromise.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 5 insertions, 3 deletions

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index e0e134d6baba..9147b8524d05 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -366,7 +366,8 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, u32 *p,
         len = args->len = ntohl(*p++);
 
         hdr = (void*)p - rqstp->rq_arg.head[0].iov_base;
-        if (rqstp->rq_arg.len < len + hdr)
+        if (rqstp->rq_arg.len < hdr ||
+            rqstp->rq_arg.len - hdr < len)
                 return 0;
 
         args->vec[0].iov_base = (void*)p;
diff --git a/include/linux/nfsd/xdr3.h b/include/linux/nfsd/xdr3.h
index 21e18ce7ca63..3c2a71b43bac 100644
--- a/include/linux/nfsd/xdr3.h
+++ b/include/linux/nfsd/xdr3.h
@@ -42,7 +42,7 @@ struct nfsd3_writeargs {
         __u64                   offset;
         __u32                   count;
         int                     stable;
-        int                     len;
+        __u32                   len;
         struct kvec             vec[RPCSVC_MAXPAGES];
         int                     vlen;
 };
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 5af8800e0ce3..e4086ec8b952 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -171,7 +171,8 @@ xdr_argsize_check(struct svc_rqst *rqstp, u32 *p)
 {
         char *cp = (char *)p;
         struct kvec *vec = &rqstp->rq_arg.head[0];
-        return cp - (char*)vec->iov_base <= vec->iov_len;
+        return cp >= (char*)vec->iov_base
+                && cp <= (char*)vec->iov_base + vec->iov_len;
 }
 
 static inline int