qemu: Make sure qemu can access its directory in hugetlbfs

When libvirtd is started, we create "libvirt/qemu" directories under
hugetlbfs mount point. Only the "qemu" subdirectory is chowned to qemu
user and "libvirt" remains owned by root. If umask was too restrictive
when libvirtd started, qemu user may lose access to "qemu"
subdirectory. Let's explicitly grant search permissions to "libvirt"
directory for all users.

src/libvirt_private.syms

@@ -1209,6 +1209,7 @@ virFileFclose;
 virFileFdopen;
 virFileRewrite;
 virFileTouch;
+virFileUpdatePerm;
 
 
 # virkeycode.h

src/qemu/qemu_driver.c

@@ -456,6 +456,8 @@ qemudStartup(int privileged) {
     int rc;
     virConnectPtr conn = NULL;
     char ebuf[1024];
+    char *membase = NULL;
+    char *mempath = NULL;
 
     if (VIR_ALLOC(qemu_driver) < 0)
         return -1;
@@ -660,23 +662,26 @@ qemudStartup(int privileged) {
      */
     if (qemu_driver->hugetlbfs_mount &&
         qemu_driver->hugetlbfs_mount[0] == '/') {
-        char *mempath = NULL;
-        if (virAsprintf(&mempath, "%s/libvirt/qemu", qemu_driver->hugetlbfs_mount) < 0)
+        if (virAsprintf(&membase, "%s/libvirt",
+                        qemu_driver->hugetlbfs_mount) < 0 ||
+            virAsprintf(&mempath, "%s/qemu", membase) < 0)
             goto out_of_memory;
 
         if (virFileMakePath(mempath) < 0) {
             virReportSystemError(errno,
                                  _("unable to create hugepage path %s"), mempath);
-            VIR_FREE(mempath);
             goto error;
         }
-        if (qemu_driver->privileged &&
-            chown(mempath, qemu_driver->user, qemu_driver->group) < 0) {
-            virReportSystemError(errno,
-                                 _("unable to set ownership on %s to %d:%d"),
-                                 mempath, qemu_driver->user, qemu_driver->group);
-            VIR_FREE(mempath);
-            goto error;
+        if (qemu_driver->privileged) {
+            if (virFileUpdatePerm(membase, 0, S_IXGRP | S_IXOTH) < 0)
+                goto error;
+            if (chown(mempath, qemu_driver->user, qemu_driver->group) < 0) {
+                virReportSystemError(errno,
+                                     _("unable to set ownership on %s to %d:%d"),
+                                     mempath, qemu_driver->user,
+                                     qemu_driver->group);
+                goto error;
+            }
         }
 
         qemu_driver->hugepage_path = mempath;
@@ -737,6 +742,8 @@ error:
         virConnectClose(conn);
     VIR_FREE(base);
     VIR_FREE(driverConf);
+    VIR_FREE(membase);
+    VIR_FREE(mempath);
     qemudShutdown();
     return -1;
 }

src/util/virfile.c

@@ -437,3 +437,40 @@ int virFileTouch(const char *path, mode_t mode)
 
     return 0;
 }
+
+
+#define MODE_BITS (S_ISUID | S_ISGID | S_ISVTX | S_IRWXU | S_IRWXG | S_IRWXO)
+
+int virFileUpdatePerm(const char *path,
+                      mode_t mode_remove,
+                      mode_t mode_add)
+{
+    struct stat sb;
+    mode_t mode;
+
+    if (mode_remove & ~MODE_BITS || mode_add & ~MODE_BITS) {
+        virFileError(VIR_ERR_INVALID_ARG, "%s", _("invalid mode"));
+        return -1;
+    }
+
+    if (stat(path, &sb) < 0) {
+        virReportSystemError(errno, _("cannot stat '%s'"), path);
+        return -1;
+    }
+
+    mode = sb.st_mode & MODE_BITS;
+
+    if ((mode & mode_remove) == 0 && (mode & mode_add) == mode_add)
+        return 0;
+
+    mode &= MODE_BITS ^ mode_remove;
+    mode |= mode_add;
+
+    if (chmod(path, mode) < 0) {
+        virReportSystemError(errno, _("cannot change permission of '%s'"),
+                             path);
+        return -1;
+    }
+
+    return 0;
+}

src/util/virfile.h

@@ -83,4 +83,8 @@ int virFileRewrite(const char *path,
 
 int virFileTouch(const char *path, mode_t mode);
 
+int virFileUpdatePerm(const char *path,
+                      mode_t mode_remove,
+                      mode_t mode_add);
+
 #endif /* __VIR_FILES_H */