[PATCH] virt-aa-helper: Avoid using RUNSTATEDIR

[Michal Privoznik <mprivozn@xxxxxxxxxx>]

On some systems /run is mounted as:

  tmpfs on /run type tmpfs (rw,nosuid,nodev,noexec,relatime,size=348508k,mode=755,inode64)

and /var/run is then just a symlink:

  # ls -ld /var/run
  lrwxrwxrwx 1 root root 4 Apr 23  2024 /var/run -> /run

But because we still think it's 2004 and FHS 2.3 is active we
have a rule in our meson.build which constructs RUNSTATEDIR as
the following:

  runstatedir = get_option('runstatedir')
  if runstatedir == ''
    runstatedir = localstatedir / 'run'
  endif

which (if unspecified on meson setup line) results in "/var/run".

This in turn means, when when we're generating an AppArmor
profile for a domain with allowed paths it contains stuff like:

  /var/run/libvirt/qemu/swtpm/2-guest-swtpm.sock

But because of the aforementioned symlink the real path is:

  /run/libvirt/qemu/swtpm/2-guest-swtpm.sock

and thus AppArmor denies access:

  audit: type=1400 audit(1740480419.348:415): apparmor="DENIED" operation="connect" class="file" profile="libvirt-126f2720-6f8e-45ab-a886-ec9277079a67" name="/run/libvirt/qemu/swtpm/2-guest-swtpm.sock" pid=8080 comm="qemu-system-x86" requested_mask="wr" denied_mask="wr" fsuid=64055 ouid=64055

Fortunately, there's a nice trick: AppArmor profile variables. We
already use some of them (@{PROC}, @{HOME}, @{multiarch}) and
instead of RUNSTATEDIR we can use @{run} which is declared as:

  # cat /etc/apparmor.d/tunables/run
  @{run}=/run/ /var/run/

and thus covers both scenarios.

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 src/security/virt-aa-helper.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/security/virt-aa-helper.c b/src/security/virt-aa-helper.c
index c255b64f35..eabc29e9cf 100644
--- a/src/security/virt-aa-helper.c
+++ b/src/security/virt-aa-helper.c
@@ -1238,8 +1238,8 @@ get_files(vahControl * ctl)
 
             /* Unix socket for QEMU and swtpm to use */
             virBufferAsprintf(&buf,
-                "  \"%s/libvirt/qemu/swtpm/%s-swtpm.sock\" rw,\n",
-                RUNSTATEDIR, shortName);
+                "  \"@{run}/libvirt/qemu/swtpm/%s-swtpm.sock\" rw,\n",
+                shortName);
             /* Paths for swtpm to use: give it access to its state
              * directory (state files and fsync on dir), log, and PID files.
              */
@@ -1253,8 +1253,8 @@ get_files(vahControl * ctl)
                 "  \"%s/log/swtpm/libvirt/qemu/%s-swtpm.log\" w,\n",
                 LOCALSTATEDIR, ctl->def->name);
             virBufferAsprintf(&buf,
-                "  \"%s/libvirt/qemu/swtpm/%s-swtpm.pid\" rw,\n",
-                RUNSTATEDIR, shortName);
+                "  \"@{run}/libvirt/qemu/swtpm/%s-swtpm.pid\" rw,\n",
+                shortName);
 
             VIR_FREE(shortName);
         }
@@ -1528,10 +1528,10 @@ main(int argc, char **argv)
                                   LOCALSTATEDIR, ctl->def->name);
                 virBufferAsprintf(&buf, "  \"%s/lib/libvirt/qemu/domain-%d-%.*s/*\" rw,\n",
                                   LOCALSTATEDIR, ctl->def->id, 20, ctl->def->name);
-                virBufferAsprintf(&buf, "  \"%s/libvirt/**/%s.pid\" rwk,\n",
-                                  RUNSTATEDIR, ctl->def->name);
-                virBufferAsprintf(&buf, "  \"%s/libvirt/**/*.tunnelmigrate.dest.%s\" rw,\n",
-                                  RUNSTATEDIR, ctl->def->name);
+                virBufferAsprintf(&buf, "  \"@{run}/libvirt/**/%s.pid\" rwk,\n",
+                                  ctl->def->name);
+                virBufferAsprintf(&buf, "  \"@{run}/libvirt/**/*.tunnelmigrate.dest.%s\" rw,\n",
+                                  ctl->def->name);
             }
             if (ctl->files)
                 virBufferAdd(&buf, ctl->files, -1);
-- 
2.45.3