NFS: Avoid memcpy() run-time warning for struct sockaddr overflows

The 'nfs_server' and 'mount_server' structures include a union of
'struct sockaddr' (with the older 16 bytes max address size) and
'struct sockaddr_storage' which is large enough to hold all the
supported sa_family types (128 bytes max size). The runtime memcpy()
buffer overflow checker is seeing attempts to write beyond the 16
bytes as an overflow, but the actual expected size is that of 'struct
sockaddr_storage'. Plumb the use of 'struct sockaddr_storage' more
completely through-out NFS, which results in adjusting the memcpy()
buffers to the correct union members. Avoids this false positive run-time
warning under CONFIG_FORTIFY_SOURCE:

  memcpy: detected field-spanning write (size 28) of single field "&ctx->nfs_server.address" at fs/nfs/namespace.c:178 (size 16)

Reported-by: kernel test robot <yujie.liu@intel.com>
Link: https://lore.kernel.org/all/202210110948.26b43120-yujie.liu@intel.com
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: linux-nfs@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
index 4da701fd1424..09833ec102fc 100644
--- a/fs/nfs/fs_context.c
+++ b/fs/nfs/fs_context.c
@@ -273,9 +273,9 @@ static const struct constant_table nfs_secflavor_tokens[] = {
  * Address family must be initialized, and address must not be
  * the ANY address for that family.
  */
-static int nfs_verify_server_address(struct sockaddr *addr)
+static int nfs_verify_server_address(struct sockaddr_storage *addr)
 {
-	switch (addr->sa_family) {
+	switch (addr->ss_family) {
 	case AF_INET: {
 		struct sockaddr_in *sa = (struct sockaddr_in *)addr;
 		return sa->sin_addr.s_addr != htonl(INADDR_ANY);
@@ -969,7 +969,7 @@ static int nfs23_parse_monolithic(struct fs_context *fc,
 {
 	struct nfs_fs_context *ctx = nfs_fc2context(fc);
 	struct nfs_fh *mntfh = ctx->mntfh;
-	struct sockaddr *sap = (struct sockaddr *)&ctx->nfs_server.address;
+	struct sockaddr_storage *sap = &ctx->nfs_server._address;
 	int extra_flags = NFS_MOUNT_LEGACY_INTERFACE;
 	int ret;
 
@@ -1044,7 +1044,7 @@ static int nfs23_parse_monolithic(struct fs_context *fc,
 		memcpy(sap, &data->addr, sizeof(data->addr));
 		ctx->nfs_server.addrlen = sizeof(data->addr);
 		ctx->nfs_server.port = ntohs(data->addr.sin_port);
-		if (sap->sa_family != AF_INET ||
+		if (sap->ss_family != AF_INET ||
 		    !nfs_verify_server_address(sap))
 			goto out_no_address;
 
@@ -1200,7 +1200,7 @@ static int nfs4_parse_monolithic(struct fs_context *fc,
 				 struct nfs4_mount_data *data)
 {
 	struct nfs_fs_context *ctx = nfs_fc2context(fc);
-	struct sockaddr *sap = (struct sockaddr *)&ctx->nfs_server.address;
+	struct sockaddr_storage *sap = &ctx->nfs_server._address;
 	int ret;
 	char *c;
 
@@ -1314,7 +1314,7 @@ static int nfs_fs_context_validate(struct fs_context *fc)
 {
 	struct nfs_fs_context *ctx = nfs_fc2context(fc);
 	struct nfs_subversion *nfs_mod;
-	struct sockaddr *sap = (struct sockaddr *)&ctx->nfs_server.address;
+	struct sockaddr_storage *sap = &ctx->nfs_server._address;
 	int max_namelen = PAGE_SIZE;
 	int max_pathlen = NFS_MAXPATHLEN;
 	int port = 0;
@@ -1540,7 +1540,7 @@ static int nfs_init_fs_context(struct fs_context *fc)
 		ctx->version		= nfss->nfs_client->rpc_ops->version;
 		ctx->minorversion	= nfss->nfs_client->cl_minorversion;
 
-		memcpy(&ctx->nfs_server.address, &nfss->nfs_client->cl_addr,
+		memcpy(&ctx->nfs_server._address, &nfss->nfs_client->cl_addr,
 			ctx->nfs_server.addrlen);
 
 		if (fc->net_ns != net) {