From fb3d8e295473034a271f09c6ce46f9500fcfa2c5 Mon Sep 17 00:00:00 2001

Message-Id: <fb3d8e295473034a271f09c6ce46f9500fcfa2c5@dist-git>

From: Michal Privoznik <mprivozn@redhat.com>

Date: Mon, 8 Mar 2021 12:57:34 +0100

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

 /dev/mapper/control

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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)

I had to replace g_strerror() from the original commit with

virStrerror() which is what we use in downstream.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1933557

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

Message-Id: <8e45903b261c50d92cea4bf3d87f724a262c928f.1615203117.git.mprivozn@redhat.com>

Reviewed-by: Ján Tomko <jtomko@redhat.com>

---

 src/util/virdevmapper.c | 25 +++++++++++++++++--------

 1 file changed, 17 insertions(+), 8 deletions(-)

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

index a76fe95922..a04d9650a6 100644

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

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

@@ -38,9 +38,12 @@

 # 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

@@ -134,11 +137,17 @@ 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;

+        char ebuf[1024];

+

+        /* 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, virStrerror(errno, ebuf, sizeof(ebuf)));

+        }

+        return -2;

     }

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

@@ -323,9 +332,9 @@ 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;

         }

-- 

2.31.0