virtio-9p: Hide user.virtfs xattr in case of mapped security.

With mapped security mode we use "user.virtfs" namespace is used
to store the virtFs related attributes. So hide it from user.
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

hw/virtio-9p-local.c

@@ -477,18 +477,87 @@ static int local_statfs(FsContext *s, const char *path, struct statfs *stbuf)
 static ssize_t local_lgetxattr(FsContext *ctx, const char *path,
                                const char *name, void *value, size_t size)
 {
+    if ((ctx->fs_sm == SM_MAPPED) &&
+        (strncmp(name, "user.virtfs.", 12) == 0)) {
+        /*
+         * Don't allow fetch of user.virtfs namesapce
+         * in case of mapped security
+         */
+        errno = ENOATTR;
+        return -1;
+    }
+
     return lgetxattr(rpath(ctx, path), name, value, size);
 }
 
 static ssize_t local_llistxattr(FsContext *ctx, const char *path,
                                 void *value, size_t size)
 {
-    return llistxattr(rpath(ctx, path), value, size);
+    ssize_t retval;
+    ssize_t actual_len = 0;
+    char *orig_value, *orig_value_start;
+    char *temp_value, *temp_value_start;
+    ssize_t xattr_len, parsed_len = 0, attr_len;
+
+    if (ctx->fs_sm != SM_MAPPED) {
+        return llistxattr(rpath(ctx, path), value, size);
+    }
+
+    /* Get the actual len */
+    xattr_len = llistxattr(rpath(ctx, path), value, 0);
+
+    /* Now fetch the xattr and find the actual size */
+    orig_value = qemu_malloc(xattr_len);
+    xattr_len = llistxattr(rpath(ctx, path), orig_value, xattr_len);
+
+    /*
+     * For mapped security model drop user.virtfs namespace
+     * from the list
+     */
+    temp_value = qemu_mallocz(xattr_len);
+    temp_value_start = temp_value;
+    orig_value_start = orig_value;
+    while (xattr_len > parsed_len) {
+        attr_len = strlen(orig_value) + 1;
+        if (strncmp(orig_value, "user.virtfs.", 12) != 0) {
+            /* Copy this entry */
+            strcat(temp_value, orig_value);
+            temp_value  += attr_len;
+            actual_len += attr_len;
+        }
+        parsed_len += attr_len;
+        orig_value += attr_len;
+    }
+    if (!size) {
+        retval = actual_len;
+        goto out;
+    } else if (size >= actual_len) {
+        /* now copy the parsed attribute list back */
+        memset(value, 0, size);
+        memcpy(value, temp_value_start, actual_len);
+        retval = actual_len;
+        goto out;
+    }
+    errno = ERANGE;
+    retval = -1;
+out:
+    qemu_free(orig_value_start);
+    qemu_free(temp_value_start);
+    return retval;
 }
 
 static int local_lsetxattr(FsContext *ctx, const char *path, const char *name,
                            void *value, size_t size, int flags)
 {
+    if ((ctx->fs_sm == SM_MAPPED) &&
+        (strncmp(name, "user.virtfs.", 12) == 0)) {
+        /*
+         * Don't allow fetch of user.virtfs namesapce
+         * in case of mapped security
+         */
+        errno = EACCES;
+        return -1;
+    }
     return lsetxattr(rpath(ctx, path), name, value, size, flags);
 }