[PATCH pve-storage 2/2] fix #6050: cifs: normalize share and subdir paths for mount and status

[David Riley <d.riley@proxmox.com>]

Manual edits to the storage configuration bypass strict API
validation. If a user adds extra or trailing slashes to the share or
subdirectory paths, it causes two distinct issues for CIFS storages:

* The Linux VFS CIFS module expects strict UNC [0] formatting and
  will reject the mount attempt with a 'Malformed UNC in devname'
  error.
* The internal path used by the status daemon fails to match the
  normalized path reported in /proc/mounts, causing working storages
  to continuously report as 'inactive'.

Sanitize the share and subdirectory strings by stripping leading and
trailing slashes before executing mounts, verifying mount status, and
testing the SMB connection. This ensures working storages mount
successfully and are correctly recognized as active.

[0] https://docs.kernel.org/admin-guide/cifs/usage.html#cifs-vfs-mount-options

Link: https://bugzilla.proxmox.com/show_bug.cgi?id=6050
Signed-off-by: David Riley <d.riley@proxmox.com>
---
 src/PVE/Storage/CIFSPlugin.pm | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/src/PVE/Storage/CIFSPlugin.pm b/src/PVE/Storage/CIFSPlugin.pm
index 54f0f4e..78ed88c 100644
--- a/src/PVE/Storage/CIFSPlugin.pm
+++ b/src/PVE/Storage/CIFSPlugin.pm
@@ -2,15 +2,20 @@ package PVE::Storage::CIFSPlugin;
 
 use strict;
 use warnings;
+
+use File::Path;
 use Net::IP;
+
 use PVE::Tools qw(run_command);
 use PVE::ProcFSTools;
-use File::Path;
 use PVE::Storage::Plugin;
 use PVE::JSONSchema qw(get_standard_option);
 
 use base qw(PVE::Storage::Plugin);
 
+my $RM_LEADING_SLASHES = qr{^/+};
+my $RM_TRAILING_SLASHES = qr{/+$};
+
 # CIFS helper functions
 
 sub cifs_is_mounted : prototype($$) {
@@ -19,8 +24,16 @@ sub cifs_is_mounted : prototype($$) {
     my ($mountpoint, $server, $share) = $scfg->@{ 'path', 'server', 'share' };
     my $subdir = $scfg->{subdir} // '';
 
+    for my $path ($share, $subdir) {
+        $path =~ s/$RM_LEADING_SLASHES// if $path;
+        $path =~ s/$RM_TRAILING_SLASHES// if $path;
+    }
+
     $server = "[$server]" if Net::IP::ip_is_ipv6($server);
-    my $source = "//${server}/$share$subdir";
+    my $source = "//${server}";
+    $source .= "/$share";
+    $source .= "/$subdir" if $subdir;
+
     $mountdata = PVE::ProcFSTools::parse_proc_mounts() if !$mountdata;
 
     return $mountpoint if grep {
@@ -83,8 +96,15 @@ sub cifs_mount : prototype($$$$$) {
     my ($mountpoint, $server, $share, $options) = $scfg->@{ 'path', 'server', 'share', 'options' };
     my $subdir = $scfg->{subdir} // '';
 
+    for my $path ($share, $subdir) {
+        $path =~ s/$RM_LEADING_SLASHES// if $path;
+        $path =~ s/$RM_TRAILING_SLASHES// if $path;
+    }
+
     $server = "[$server]" if Net::IP::ip_is_ipv6($server);
-    my $source = "//${server}/$share$subdir";
+    my $source = "//${server}";
+    $source .= "/$share";
+    $source .= "/$subdir" if $subdir;
 
     my $cmd = ['/bin/mount', '-t', 'cifs', $source, $mountpoint, '-o', 'soft'];
 
@@ -285,7 +305,11 @@ sub deactivate_storage {
 sub check_connection {
     my ($class, $storeid, $scfg) = @_;
 
-    my $servicename = '//' . $scfg->{server} . '/' . $scfg->{share};
+    my $share = $scfg->{share};
+    $share =~ s/$RM_LEADING_SLASHES// if $share;
+    $share =~ s/$RM_TRAILING_SLASHES// if $share;
+
+    my $servicename = '//' . $scfg->{server} . '/' . $share;
 
     my $cmd = ['/usr/bin/smbclient', $servicename, '-d', '0'];
 
-- 
2.47.3