Avoid beyond bounds copy while caching ACL

When attempting to cache ACLs returned from the server, if the bitmap
size + the ACL size is greater than a PAGE_SIZE but the ACL size itself
is smaller than a PAGE_SIZE, we can read past the buffer page boundary.
Signed-off-by: NSachin Prabhu <sprabhu@redhat.com>
Reported-by: NJian Li <jiali@redhat.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -3628,16 +3628,16 @@ static inline ssize_t nfs4_read_cached_acl(struct inode *inode, char *buf, size_
 	return ret;
 }
 
-static void nfs4_write_cached_acl(struct inode *inode, const char *buf, size_t acl_len)
+static void nfs4_write_cached_acl(struct inode *inode, struct page **pages, size_t pgbase, size_t acl_len)
 {
 	struct nfs4_cached_acl *acl;
 
-	if (buf && acl_len <= PAGE_SIZE) {
+	if (pages && acl_len <= PAGE_SIZE) {
 		acl = kmalloc(sizeof(*acl) + acl_len, GFP_KERNEL);
 		if (acl == NULL)
 			goto out;
 		acl->cached = 1;
-		memcpy(acl->data, buf, acl_len);
+		_copy_from_pages(acl->data, pages, pgbase, acl_len);
 	} else {
 		acl = kmalloc(sizeof(*acl), GFP_KERNEL);
 		if (acl == NULL)
@@ -3670,7 +3670,6 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 	struct nfs_getaclres res = {
 		.acl_len = buflen,
 	};
-	void *resp_buf;
 	struct rpc_message msg = {
 		.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_GETACL],
 		.rpc_argp = &args,
@@ -3705,7 +3704,6 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 	 * the page we send as a guess */
 	if (buf == NULL)
 		res.acl_flags |= NFS4_ACL_LEN_REQUEST;
-	resp_buf = page_address(pages[0]);
 
 	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
 		__func__, buf, buflen, npages, args.acl_len);
@@ -3716,9 +3714,9 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
 
 	acl_len = res.acl_len - res.acl_data_offset;
 	if (acl_len > args.acl_len)
-		nfs4_write_cached_acl(inode, NULL, acl_len);
+		nfs4_write_cached_acl(inode, NULL, 0, acl_len);
 	else
-		nfs4_write_cached_acl(inode, resp_buf + res.acl_data_offset,
+		nfs4_write_cached_acl(inode, pages, res.acl_data_offset,
 				      acl_len);
 	if (buf) {
 		ret = -ERANGE;

fs/nfs/nfs4xdr.c

@@ -4940,7 +4940,7 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
 				res->acl_len = attrlen;
 				goto out;
 			}
-			dprintk("NFS: acl reply: attrlen %zu > page_len %u\n",
+			dprintk("NFS: acl reply: attrlen %u > page_len %zu\n",
 					attrlen, page_len);
 			return -EINVAL;
 		}