conf: fix read-only bind mounts

Here we would always set MS_RDONLY in required_flags if it was set in
mountflags, so the expression:

!(required_flags & ~mountflags)

would always be true, and we would always skip the remount.

Instead, let's treat readonly as special: always do the remount if
MS_RDONLY is present. Unfortunately it doesn't seem to show up in
sb.f_flag, so we can't use the same path as everything else.

This only inadvertently worked before because of a bug fixed in
f75917858023 ("conf: don't accidently double-mount").

Signed-off-by: Tycho Andersen <tycho@tycho.ws>

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 2de772511e50754663977eae3fab044afaaf2287..0c36737c6151148054cf6a454b0e52f4d67aa23b 100644 (file)
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -1847,15 +1847,14 @@ static int mount_entry(const char *fsname, const char *target,
        }
 
        if ((mountflags & MS_REMOUNT) || (mountflags & MS_BIND)) {
-               unsigned long required_flags = 0;
 
                DEBUG("Remounting \"%s\" on \"%s\" to respect bind or remount options",
                      srcpath ? srcpath : "(none)", target ? target : "(none)");
 
-               if (mountflags & MS_RDONLY)
-                       required_flags |= MS_RDONLY;
 #ifdef HAVE_STATVFS
                if (srcpath && statvfs(srcpath, &sb) == 0) {
+                       unsigned long required_flags = 0;
+
                        if (sb.f_flag & MS_NOSUID)
                                required_flags |= MS_NOSUID;
 
@@ -1875,7 +1874,8 @@ static int mount_entry(const char *fsname, const char *target,
                         * does not have any flags which are not already in
                         * mountflags, then skip the remount.
                         */
-                       if (!(mountflags & MS_REMOUNT) && !(required_flags & ~mountflags)) {
+                       if (!(mountflags & MS_REMOUNT) &&
+                           (!(required_flags & ~mountflags) && !(mountflags & MS_RDONLY))) {
                                DEBUG("Mountflags already were %lu, skipping remount", mountflags);
                                goto skipremount;
                        }