nfsd: stricter decoding of write-like NFSv2/v3 ops

commit 13bf9fbff0e5e099e2b6f003a0ab8ae145436309 upstream.

The NFSv2/v3 code does not systematically check whether we decode past
the end of the buffer.  This generally appears to be harmless, but there
are a few places where we do arithmetic on the pointers involved and
don't account for the possibility that a length could be negative.  Add
checks to catch these.

Reported-by: Tuomas Haanpää <thaan@synopsys.com>
Reported-by: Ari Kauppi <ari@synopsys.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index f7be384..7b382f8 100644 (file)
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -363,6 +363,8 @@ nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
        args->count = ntohl(*p++);
        args->stable = ntohl(*p++);
        len = args->len = ntohl(*p++);
        args->count = ntohl(*p++);
        args->stable = ntohl(*p++);
        len = args->len = ntohl(*p++);

+       if ((void *)p > head->iov_base + head->iov_len)
+               return 0;

        /*
         * The count must equal the amount of data passed.
         */
        /*
         * The count must equal the amount of data passed.
         */


@@ -467,6 +469,8 @@ nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p,
        /* first copy and check from the first page */
        old = (char*)p;
        vec = &rqstp->rq_arg.head[0];
        /* first copy and check from the first page */
        old = (char*)p;
        vec = &rqstp->rq_arg.head[0];

+       if ((void *)old > vec->iov_base + vec->iov_len)
+               return 0;

        avail = vec->iov_len - (old - (char*)vec->iov_base);
        while (len && avail && *old) {
                *new++ = *old++;
        avail = vec->iov_len - (old - (char*)vec->iov_base);
        while (len && avail && *old) {
                *new++ = *old++;

diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
index 5ca1561..830f29b 100644 (file)
--- a/fs/nfsd/nfsxdr.c
+++ b/fs/nfsd/nfsxdr.c
@@ -298,6 +298,8 @@ nfssvc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p,
         * bytes.
         */
        hdr = (void*)p - head->iov_base;
         * bytes.
         */
        hdr = (void*)p - head->iov_base;

+       if (hdr > head->iov_len)
+               return 0;

        dlen = head->iov_len + rqstp->rq_arg.page_len - hdr;
 
        /*
        dlen = head->iov_len + rqstp->rq_arg.page_len - hdr;
 
        /*