[pve-devel] [PATCH container] fix #5907: ignore conflicting mount options for read-only mounts

[Filip Schauer]

When mounting volumes as read-only, certain mount options like
"discard", "lazytime", and "noatime" are either ignored or can cause the
mount to fail. For example, attempting to mount with "-t zfs" and
"-o ro,discard" leads to an error: filesystem cannot be mounted due to
invalid option 'discard'.

This commit ensures that only valid mount options, such as "nodev",
"noexec", and "nosuid", are applied to read-only mounts, avoiding
potential mount failures.

Signed-off-by: Filip Schauer <f.schauer at proxmox.com>
---
 src/PVE/LXC.pm        | 8 ++++++--
 src/PVE/LXC/Config.pm | 6 ++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index e78e365..d01fafc 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -1865,11 +1865,16 @@ sub __mountpoint_mount {
 
     die "unknown snapshot path for '$volid'" if !$storage && defined($snapname);
 
+    my $readonly = $mountpoint->{ro};
     my $optlist = [];
 
     if (my $mountopts = $mountpoint->{mountoptions}) {
 	my @opts = split(/;/, $mountpoint->{mountoptions});
-	push @$optlist, grep { PVE::LXC::Config::is_valid_mount_option($_) } @opts;
+	if ($readonly || defined($snapname)) {
+	    push @$optlist, grep { PVE::LXC::Config::is_valid_ro_mount_option($_) } @opts;
+	} else {
+	    push @$optlist, grep { PVE::LXC::Config::is_valid_mount_option($_) } @opts;
+	}
     }
 
     my $acl = $mountpoint->{acl};
@@ -1880,7 +1885,6 @@ sub __mountpoint_mount {
     }
 
     my $optstring = join(',', @$optlist);
-    my $readonly = $mountpoint->{ro};
 
     my @extra_opts;
     @extra_opts = ('-o', $optstring) if $optstring;
diff --git a/src/PVE/LXC/Config.pm b/src/PVE/LXC/Config.pm
index 5cc37f7..0740e8c 100644
--- a/src/PVE/LXC/Config.pm
+++ b/src/PVE/LXC/Config.pm
@@ -312,12 +312,18 @@ cfs_register_file('/lxc/', \&parse_pct_config, \&write_pct_config);
 
 
 my $valid_mount_option_re = qr/(discard|lazytime|noatime|nodev|noexec|nosuid)/;
+my $valid_ro_mount_option_re = qr/(nodev|noexec|nosuid)/;
 
 sub is_valid_mount_option {
     my ($option) = @_;
     return $option =~ $valid_mount_option_re;
 }
 
+sub is_valid_ro_mount_option {
+    my ($option) = @_;
+    return $option =~ $valid_ro_mount_option_re;
+}
+
 my $rootfs_desc = {
     volume => {
 	type => 'string',
-- 
2.39.5