[libvirt] [PATCH] xen: fix memory corruption in legacy driver

[Jim Fehlig]

Commit 632180d1 introduced memory corruption in xenDaemonListDefinedDomains
by starting to populate the names array at index -1, causing all sorts
of havoc in libvirtd such as aborts like the following

*** Error in `/usr/sbin/libvirtd': double free or corruption (out): 0x00007fffe00ccf20 ***
======= Backtrace: =========
/lib64/libc.so.6(+0x7abf6)[0x7ffff3fa0bf6]
/lib64/libc.so.6(+0x7b973)[0x7ffff3fa1973]
/lib64/libc.so.6(xdr_array+0xde)[0x7ffff403cbae]
/usr/sbin/libvirtd(+0x50251)[0x5555555a4251]
/lib64/libc.so.6(xdr_free+0x15)[0x7ffff403ccd5]
/usr/lib64/libvirt.so.0(+0x1fad34)[0x7ffff76b1d34]
/usr/lib64/libvirt.so.0(virNetServerProgramDispatch+0x1fc)[0x7ffff76b16f1]
/usr/lib64/libvirt.so.0(+0x1f214a)[0x7ffff76a914a]
/usr/lib64/libvirt.so.0(+0x1f222d)[0x7ffff76a922d]
/usr/lib64/libvirt.so.0(+0xbcc4f)[0x7ffff7573c4f]
/usr/lib64/libvirt.so.0(+0xbc5e5)[0x7ffff75735e5]
/lib64/libpthread.so.0(+0x7e0f)[0x7ffff48f7e0f]
/lib64/libc.so.6(clone+0x6d)[0x7ffff400e7dd]

Fix by initializing ret to 0 and only setting to error on failure path.
---
 src/xen/xend_internal.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/xen/xend_internal.c b/src/xen/xend_internal.c
index 1ce36e6..f698c8d 100644
--- a/src/xen/xend_internal.c
+++ b/src/xen/xend_internal.c
@@ -2896,7 +2896,7 @@ xenDaemonListDefinedDomains(virConnectPtr conn,
 {
     struct sexpr *root = NULL;
     size_t i;
-    int ret = -1;
+    int ret = 0;
     struct sexpr *_for_i, *node;
 
     if (maxnames == 0)
@@ -2919,16 +2919,15 @@ xenDaemonListDefinedDomains(virConnectPtr conn,
             break;
     }
 
-    ret = 0;
-
 cleanup:
     sexpr_free(root);
     return ret;
 
 error:
-    for (i = 0; ret != -1 && i < ret; ++i)
+    for (i = 0; i < ret; ++i)
         VIR_FREE(names[i]);
 
+    ret = -1;
     goto cleanup;
 }
 
-- 
1.8.1.4