From b38ab86a0a2cf3453d37a5fe96b2e022d8a1d48a Mon Sep 17 00:00:00 2001

Message-Id: <b38ab86a0a2cf3453d37a5fe96b2e022d8a1d48a@dist-git>

From: Michal Privoznik <mprivozn@redhat.com>

Date: Tue, 25 Aug 2020 17:16:07 +0200

Subject: [PATCH] virdevmapper: Ignore all errors when opening

 /dev/mapper/control

So far, only ENOENT is ignored (to deal with kernels without

devmapper). However, as reported on the list, under certain

scenarios a different error can occur. For instance, when libvirt

is running inside a container which doesn't have permissions to

talk to the devmapper. If this is the case, then open() returns

-1 and sets errno=EPERM.

Assuming that multipath devices are fairly narrow use case and

using them in a restricted container is even more narrow the best

fix seems to be to ignore all open errors BUT produce a warning

on failure. To avoid flooding logs with warnings on kernels

without devmapper the level is reduced to a plain debug message.

Reported-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>

Reviewed-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

(cherry picked from commit 53d9af1e7924757e3b5f661131dd707d7110d094)

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1860421

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

Message-Id: <e1b69d69e7d242829995208c6d59ed0477208920.1598364552.git.mprivozn@redhat.com>

Reviewed-by: Jiri Denemark <jdenemar@redhat.com>

---

 src/util/virdevmapper.c | 23 +++++++++++++++--------

 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/util/virdevmapper.c b/src/util/virdevmapper.c

index a81e2edee4..ee2fab5ae3 100644

--- a/src/util/virdevmapper.c

+++ b/src/util/virdevmapper.c

@@ -35,9 +35,12 @@

 # include "viralloc.h"

 # include "virstring.h"

 # include "virfile.h"

+# include "virlog.h"

 # define VIR_FROM_THIS VIR_FROM_STORAGE

+VIR_LOG_INIT("util.virdevmapper");

+

 # define PROC_DEVICES "/proc/devices"

 # define DM_NAME "device-mapper"

 # define DEV_DM_DIR "/dev/" DM_DIR

@@ -130,11 +133,15 @@ virDMOpen(void)

     memset(&dm, 0, sizeof(dm));

     if ((controlFD = open(CONTROL_PATH, O_RDWR)) < 0) {

-        if (errno == ENOENT)

-            return -2;

-

-        virReportSystemError(errno, _("Unable to open %s"), CONTROL_PATH);

-        return -1;

+        /* We can't talk to devmapper. Produce a warning and let

+         * the caller decide what to do next. */

+        if (errno == ENOENT) {

+            VIR_DEBUG("device mapper not available");

+        } else {

+            VIR_WARN("unable to open %s: %s",

+                     CONTROL_PATH, g_strerror(errno));

+        }

+        return -2;

     }

     if (!virDMIoctl(controlFD, DM_VERSION, &dm, &tmp)) {

@@ -310,9 +317,9 @@ virDevMapperGetTargets(const char *path,

     if ((controlFD = virDMOpen()) < 0) {

         if (controlFD == -2) {

-            /* The CONTROL_PATH doesn't exist. Probably the

-             * module isn't loaded, yet. Don't error out, just

-             * exit. */

+            /* The CONTROL_PATH doesn't exist or is unusable.

+             * Probably the module isn't loaded, yet. Don't error

+             * out, just exit. */

             return 0;

         }

-- 

2.28.0