[libvirt] [PATCH] Fix uninitialized variable & error reporting in LXC veth setup

[Daniel P. Berrange]

On Thu, Mar 17, 2011 at 12:46:55PM -0400, Laine Stump wrote:
> On 03/17/2011 11:57 AM, Daniel P. Berrange wrote:
> >THe veth setup in LXC had a couple of flaws, first brInit did
> >not report any error when it failed. Second vethCreate() did
> >not correctly initialize the variable containing the return
> >code, so could report failure even when it succeeded.
> >
> >* src/lxc/lxc_driver.c: Report error when brInit fails
> >* src/lxc/veth.c: Fix uninitialized variable
> >---
> >  src/lxc/lxc_driver.c |    8 ++++++--
> >  src/lxc/veth.c       |   17 +++++++++--------
> >  2 files changed, 15 insertions(+), 10 deletions(-)
> >
> >diff --git a/src/lxc/lxc_driver.c b/src/lxc/lxc_driver.c
> >index 79b6879..9b131cc 100644
> >--- a/src/lxc/lxc_driver.c
> >+++ b/src/lxc/lxc_driver.c
> >@@ -1024,9 +1024,13 @@ static int lxcSetupInterfaces(virConnectPtr conn,
> >      int rc = -1, i;
> >      char *bridge = NULL;
> >      brControl *brctl = NULL;
> >+    int ret;
> >
> >-    if (brInit(&brctl) != 0)
> >+    if ((ret = brInit(&brctl)) != 0) {
> >+        virReportSystemError(ret, "%s",
> >+                             _("Unable to initialize bridging"));
> >          return -1;
> >+    }
> >
> >      for (i = 0 ; i<  def->nnets ; i++) {
> >          char *parentVeth;
> >@@ -1095,7 +1099,7 @@ static int lxcSetupInterfaces(virConnectPtr conn,
> >                  goto error_exit;
> >          }
> >
> >-        if (0 != (rc = brAddInterface(brctl, bridge, parentVeth))) {
> >+        if ((ret = brAddInterface(brctl, bridge, parentVeth)) != 0) {
> >              virReportSystemError(rc,
> >                                   _("Failed to add %s device to %s"),
> >                                   parentVeth, bridge);
> >diff --git a/src/lxc/veth.c b/src/lxc/veth.c
> >index 0fa76cf..deca26d 100644
> >--- a/src/lxc/veth.c
> >+++ b/src/lxc/veth.c
> >@@ -90,7 +90,7 @@ static int getFreeVethName(char **veth, int startDev)
> >   */
> >  int vethCreate(char** veth1, char** veth2)
> >  {
> >-    int rc;
> >+    int rc = -1;
> >      const char *argv[] = {
> >          "ip", "link", "add", NULL, "type", "veth", "peer", "name", NULL, NULL
> >      };
> >@@ -100,9 +100,8 @@ int vethCreate(char** veth1, char** veth2)
> >      VIR_DEBUG("veth1: %s veth2: %s", NULLSTR(*veth1), NULLSTR(*veth2));
> >
> >      if (*veth1 == NULL) {
> >-        vethDev = getFreeVethName(veth1, vethDev);
> >-        if (vethDev<  0)
> >-            return vethDev;
> >+        if ((vethDev = getFreeVethName(veth1, vethDev))<  0)
> >+            goto cleanup;
> >          VIR_DEBUG("Assigned veth1: %s", *veth1);
> >          veth1_alloc = true;
> >      }
> >@@ -110,11 +109,10 @@ int vethCreate(char** veth1, char** veth2)
> >
> >      while (*veth2 == NULL || STREQ(*veth1, *veth2)) {
> >          VIR_FREE(*veth2);
> >-        vethDev = getFreeVethName(veth2, vethDev + 1);
> >-        if (vethDev<  0) {
> >+        if ((vethDev = getFreeVethName(veth2, vethDev + 1))<  0) {
> >              if (veth1_alloc)
> >                  VIR_FREE(*veth1);
> 
> If you really want to put things back as they were prior to this
> function being called, shouldn't you also be doing "*veth1 = NULL;"?
> (This would also eliminate the potential of a caller doing a
> double-free.)

VIR_FREE sets the parameter back to NULL, so *veth1 = NULL
is in effect already done here.

> 
> >-            return vethDev;
> >+            goto cleanup;
> >          }
> >          VIR_DEBUG("Assigned veth2: %s", *veth2);
> >      }
> >@@ -125,9 +123,12 @@ int vethCreate(char** veth1, char** veth2)
> >          if (veth1_alloc)
> >              VIR_FREE(*veth1);
> >          VIR_FREE(*veth2);
> 
> Likewise for both of these. Additionally, if someone were to call
> vethCreate with a non-null veth2, and virRun() then failed,
> vethCreate would erroneously free *veth2 - it should also be
> protected with a "veth2_alloc".

Again VIR_FREE sets them to NULL, but we do need the
extra check here for veth2_alloc.


Daniel
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