[libvirt] [PATCH] Fix libvirtd free() segfault when migrating guest with deleted open vswitch port

libvirtd crashes on free()ing portData for an open vswitch port if that port was deleted. To reproduce: ovs-vsctl del-port vnet0 virsh migrate --live kvm1 qemu+ssh://dstHost/system Error message: libvirtd: *** Error in `/usr/sbin/libvirtd': free(): invalid pointer: 0x000003ff90001e20 *** The problem is that virCommandRun can return an empty string in the event that the port being queried does not exist. When this happens then we are unconditionally overwriting a newline character at position strlen()-1. When strlen is 0, we overwrite memory that does not belong to the string. The fix: Only overwrite the newline if the string is not empty. Reviewed-by: Bjoern Walk <bwalk(a)linux.vnet.ibm.com&gt; Signed-off-by: Jason J. Herne <jjherne(a)linux.vnet.ibm.com&gt; --- src/util/virnetdevopenvswitch.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/util/virnetdevopenvswitch.c b/src/util/virnetdevopenvswitch.c index 6780fb5..0f640d0 100644 --- a/src/util/virnetdevopenvswitch.c +++ b/src/util/virnetdevopenvswitch.c @@ -222,8 +222,10 @@ int virNetDevOpenvswitchGetMigrateData(char **migrate, const char *ifname) goto cleanup; } - /* Wipeout the newline */ - (*migrate)[strlen(*migrate) - 1] = '\0'; + /* Wipeout the newline, if it exists */ + if (strlen(*migrate) > 0) { + (*migrate)[strlen(*migrate) - 1] = '\0'; + } ret = 0; cleanup: virCommandFree(cmd); -- 1.9.1