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Re: [libvirt] [PATCH 4/4] rpc: Fix potentially segfaults



On 02/09/2017 09:13 AM, Marc Hartmayer wrote:
We have to allocate first and if, and only if, it was successful we
can set the count. A segfault has occurred in
virNetServerServiceNewPostExecRestart() when VIR_ALLOC_N(svc->socks,
n) has failed, but svc->nsocsk = n was already set. Thus
virObejectUnref(svc) was called and therefore it was possible that
virNetServerServiceDispose was called => segmentation fault.  For
safeness NULL pointer check were added in
virNetServerServiceDispose().

Signed-off-by: Marc Hartmayer <mhartmay linux vnet ibm com>
Reviewed-by: Boris Fiuczynski <fiuczy linux vnet ibm com>
Reviewed-by: Bjoern Walk <bwalk linux vnet ibm com>
---
  src/rpc/virnetserverservice.c | 20 +++++++++++---------
  1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/rpc/virnetserverservice.c b/src/rpc/virnetserverservice.c
index 1ef0636..006d041 100644
--- a/src/rpc/virnetserverservice.c
+++ b/src/rpc/virnetserverservice.c
@@ -228,9 +228,9 @@ virNetServerServicePtr virNetServerServiceNewUNIX(const char *path,
      svc->tls = virObjectRef(tls);
  #endif
- svc->nsocks = 1;
-    if (VIR_ALLOC_N(svc->socks, svc->nsocks) < 0)
+    if (VIR_ALLOC_N(svc->socks, 1) < 0)
          goto error;
+    svc->nsocks = 1;
if (virNetSocketNewListenUNIX(path,
                                    mask,
@@ -289,9 +289,9 @@ virNetServerServicePtr virNetServerServiceNewFD(int fd,
      svc->tls = virObjectRef(tls);
  #endif
- svc->nsocks = 1;
-    if (VIR_ALLOC_N(svc->socks, svc->nsocks) < 0)
+    if (VIR_ALLOC_N(svc->socks, 1) < 0)
          goto error;
+    svc->nsocks = 1;
if (virNetSocketNewListenFD(fd,
                                  &svc->socks[0]) < 0)
@@ -367,9 +367,9 @@ virNetServerServicePtr virNetServerServiceNewPostExecRestart(virJSONValuePtr obj
          goto error;
      }
- svc->nsocks = n;
-    if (VIR_ALLOC_N(svc->socks, svc->nsocks) < 0)
+    if (VIR_ALLOC_N(svc->socks, n) < 0)
          goto error;
+    svc->nsocks = n;
for (i = 0; i < svc->nsocks; i++) {
          virJSONValuePtr child = virJSONValueArrayGet(socks, i);
@@ -492,9 +492,11 @@ void virNetServerServiceDispose(void *obj)
      virNetServerServicePtr svc = obj;
      size_t i;
- for (i = 0; i < svc->nsocks; i++)
-        virObjectUnref(svc->socks[i]);
-    VIR_FREE(svc->socks);
+    if (svc->socks) {
+        for (i = 0; i < svc->nsocks; i++)
+            virObjectUnref(svc->socks[i]);
+        VIR_FREE(svc->socks);
+    }

re: your other message - we shouldn't need to check for svc->socks != NULL here (see my response to your self-response). And I *think* we don't need to worry about settinc svc->nsocks = 0 here, since the dispose function can only be called once per object.

Do you see any problem with me removing the "if (svc->socks)" around the for loop and VIR_FREE()? If not, I'll do that and push the result. (ACK, assuming that change is okay with you)



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