[libvirt] [PATCH v2] util: Fix stack smashing in virNetDevGetFamilyId

[Laine Stump]

After commit 8708ca01c0d libvirtd consistently aborts with "stack
 smashing detected" when nodedev driver is initialized.

This is caused by nlmsg_parse() being told that its array of nlattr*
has CTRL_CMD_MAX (10) entries, when in fact it is declared to have
CTRL_ATTR_MAX (8) entries. Since all the entries are initialized to
NULL, the result is that nlmsg_parse is overwriting 2*(sizof(nlattr*))
bytes outside the array.

Signed-off-by: Laine Stump <laine at laine.org>
---

V1 was posted by jdenemar. It fixed the problem, but it was changing
the wrong line of code:

  https://www.redhat.com/archives/libvir-list/2017-September/msg00657.html

 src/util/virnetdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c
index 41a659732..5060d051d 100644
--- a/src/util/virnetdev.c
+++ b/src/util/virnetdev.c
@@ -3183,7 +3183,7 @@ virNetDevGetFamilyId(const char *family_name)
     if (virNetlinkCommand(nl_msg, &resp, &recvbuflen, 0, 0, NETLINK_GENERIC, 0) < 0)
         goto cleanup;
 
-    if (nlmsg_parse(resp, sizeof(struct nlmsghdr), tb, CTRL_CMD_MAX, NULL) < 0) {
+    if (nlmsg_parse(resp, sizeof(struct nlmsghdr), tb, CTRL_ATTR_MAX, NULL) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("malformed netlink response message"));
         goto cleanup;
-- 
2.13.5