[PATCH] Honor blacklist for modprobe command

[John Ferlan <jferlan@xxxxxxxxxx>]

https://bugzilla.redhat.com/show_bug.cgi?id=1045124

When loading modules, libvirt does not honor the modprobe blacklist.
By adding a "-b" to the modprobe command libvirt will fail to load a
module if it's on the blacklist

Check if the failure to load a driver was due to it being on the blacklist
using the output of a "modprobe -c" searching for "blacklist <driver_Name>"
where driver_Name is possibly a modified string of the input driver changing
all '-' into '_' since that's what modprobe does.

Signed-off-by: John Ferlan <jferlan@xxxxxxxxxx>
---
 src/util/virpci.c | 48 ++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/src/util/virpci.c b/src/util/virpci.c
index e2d222e..18b85f2 100644
--- a/src/util/virpci.c
+++ b/src/util/virpci.c
@@ -979,6 +979,10 @@ virPCIProbeStubDriver(const char *driver)
 {
     char *drvpath = NULL;
     bool probed = false;
+    size_t i;
+    char *drvblklst = NULL;
+    char *outbuf = NULL;
+    virCommandPtr cmd = NULL;
 
 recheck:
     if (virPCIDriverDir(&drvpath, driver) == 0 && virFileExists(drvpath)) {
@@ -990,18 +994,49 @@ recheck:
     VIR_FREE(drvpath);
 
     if (!probed) {
-        const char *const probecmd[] = { MODPROBE, driver, NULL };
+        cmd = virCommandNewArgList(MODPROBE, "-b", driver, NULL);
         probed = true;
-        if (virRun(probecmd, NULL) < 0) {
+        if (virCommandRun(cmd, NULL) < 0) {
             char ebuf[1024];
             VIR_WARN("failed to load driver %s: %s", driver,
                      virStrerror(errno, ebuf, sizeof(ebuf)));
-            return -1;
+            goto cleanup;
         }
+        virCommandFree(cmd);
+        cmd = NULL;
 
         goto recheck;
     }
 
+    /* All error path code - purpose is to determine whether the failure
+     * occurs because device is on blacklist in order to add an error
+     * message to help detect why load failed
+     */
+    if (virAsprintfQuiet(&drvblklst, "blacklist %s", driver) < 0)
+        goto cleanup;
+
+    /* Although driver may have dash, 'modprobe -c' adjusts to use underscore */
+    for (i = 0; i < drvblklst[i]; i++)
+        if (drvblklst[i] == '-')
+            drvblklst[i] = '_';
+
+    cmd = virCommandNewArgList(MODPROBE, "-c", NULL);
+    virCommandSetOutputBuffer(cmd, &outbuf);
+    if (virCommandRun(cmd, NULL) < 0)
+        goto cleanup;
+
+    /* Find driver on blacklist? */
+    if (strstr(outbuf, drvblklst)) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Failed to load PCI stub module %s: "
+                         "administratively prohibited"),
+                       driver);
+    }
+
+cleanup:
+    virCommandFree(cmd);
+    VIR_FREE(drvblklst);
+    VIR_FREE(outbuf);
     return -1;
 }
 
@@ -1313,9 +1348,10 @@ virPCIDeviceDetach(virPCIDevicePtr dev,
                    virPCIDeviceList *inactiveDevs)
 {
     if (virPCIProbeStubDriver(dev->stubDriver) < 0) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("Failed to load PCI stub module %s"),
-                       dev->stubDriver);
+        if (virGetLastError() == NULL)
+            virReportError(VIR_ERR_INTERNAL_ERROR,
+                           _("Failed to load PCI stub module %s"),
+                           dev->stubDriver);
         return -1;
     }
 
-- 
1.8.4.2

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