nfsd: Limit end of page list when decoding NFSv4 WRITE

When processing an NFSv4 WRITE operation, argp->end should never
point past the end of the data in the final page of the page list.
Otherwise, nfsd4_decode_compound can walk into uninitialized memory.

More critical, nfsd4_decode_write is failing to increment argp->pagelen
when it increments argp->pagelist.  This can cause later xdr decoders
to assume more data is available than really is, which can cause server
crashes on malformed requests.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 20fbcab977531bee75501a9403f4c8f60ee404d4..5f940d2a136b72a8e5ffcbff2f094b9f0ebfdaa3 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -144,7 +144,7 @@ static void next_decode_page(struct nfsd4_compoundargs *argp)
        argp->p = page_address(argp->pagelist[0]);
        argp->pagelist++;
        if (argp->pagelen < PAGE_SIZE) {
-               argp->end = argp->p + (argp->pagelen>>2);
+               argp->end = argp->p + XDR_QUADLEN(argp->pagelen);
                argp->pagelen = 0;
        } else {
                argp->end = argp->p + (PAGE_SIZE>>2);
@@ -1279,9 +1279,7 @@ nfsd4_decode_write(struct nfsd4_compoundargs *argp, struct nfsd4_write *write)
                argp->pagelen -= pages * PAGE_SIZE;
                len -= pages * PAGE_SIZE;
 
-               argp->p = (__be32 *)page_address(argp->pagelist[0]);
-               argp->pagelist++;
-               argp->end = argp->p + XDR_QUADLEN(PAGE_SIZE);
+               next_decode_page(argp);
        }
        argp->p += XDR_QUADLEN(len);