CVE-2021-3905: Missing Release of Memory after Effective Lifetime (CWE-401)
value: A memory leak was found in Open vSwitch (OVS) during userspace IP fragmentation processing. An attacker could use this flaw to potentially exhaust available memory by keeping sending packet fragments.
CWE description: The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.
CVSS v3 base score: 7.5
Published: 2022-08-23T16:15Z
Repository: https://github.com/openvswitch/ovs
Language: C
Files changed: lib/ipf.c
Commit date: 2021-10-12 18:25:44 +0300
Commit message: ipf: release unhandled packets from the batch

Since 640d4db788ed ("ipf: Fix a use-after-free error, ...") the ipf
framework unconditionally allocates a new dp_packet to track
individual fragments.  This prevents a use-after-free.  However, an
additional issue was present - even when the packet buffer is cloned,
if the ip fragment handling code keeps it, the original buffer is
leaked during the refill loop.  Even in the original processing code,
the hardcoded dnsteal branches would always leak a packet buffer from
the refill loop.

This can be confirmed with valgrind:

==717566== 16,672 (4,480 direct, 12,192 indirect) bytes in 8 blocks are definitely lost in loss record 390 of 390
==717566==    at 0x484086F: malloc (vg_replace_malloc.c:380)
==717566==    by 0x537BFD: xmalloc__ (util.c:137)
==717566==    by 0x537BFD: xmalloc (util.c:172)
==717566==    by 0x46DDD4: dp_packet_new (dp-packet.c:153)
==717566==    by 0x46DDD4: dp_packet_new_with_headroom (dp-packet.c:163)
==717566==    by 0x550AA6: netdev_linux_batch_rxq_recv_sock.constprop.0 (netdev-linux.c:1262)
==717566==    by 0x5512AF: netdev_linux_rxq_recv (netdev-linux.c:1511)
==717566==    by 0x4AB7E0: netdev_rxq_recv (netdev.c:727)
==717566==    by 0x47F00D: dp_netdev_process_rxq_port (dpif-netdev.c:4699)
==717566==    by 0x47FD13: dpif_netdev_run (dpif-netdev.c:5957)
==717566==    by 0x4331D2: type_run (ofproto-dpif.c:370)
==717566==    by 0x41DFD8: ofproto_type_run (ofproto.c:1768)
==717566==    by 0x40A7FB: bridge_run__ (bridge.c:3245)
==717566==    by 0x411269: bridge_run (bridge.c:3310)
==717566==    by 0x406E6C: main (ovs-vswitchd.c:127)

The fix is to delete the original packet when it isn't able to be
reinserted into the packet batch.  Subsequent valgrind runs show that
the packets are not leaked from the batch any longer.

Fixes: 640d4db788ed ("ipf: Fix a use-after-free error, and remove the 'do_not_steal' flag.")
Fixes: 4ea96698f667 ("Userspace datapath: Add fragmentation handling.")
Reported-by: Wan Junjie <wanjunjie@bytedance.com>
Reported-at: https://github.com/openvswitch/ovs-issues/issues/226
Signed-off-by: Aaron Conole <aconole@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Tested-by: Wan Junjie <wanjunjie@bytedance.com>
Signed-off-by: Alin-Gabriel Serdean <aserdean@ovn.org>

Diff: diff --git a/lib/ipf.c b/lib/ipf.c
index 665f40fef..507db2aea 100644
--- a/lib/ipf.c
+++ b/lib/ipf.c
@@ -941,10 +941,12 @@ ipf_extract_frags_from_batch(struct ipf *ipf, struct dp_packet_batch *pb,
                           ipf_is_valid_v6_frag(ipf, pkt)))) {
 
             ovs_mutex_lock(&ipf->ipf_lock);
             if (!ipf_handle_frag(ipf, pkt, dl_type, zone, now, hash_basis)) {
                 dp_packet_batch_refill(pb, pkt, pb_idx);
+            } else {
+                dp_packet_delete(pkt);
             }
             ovs_mutex_unlock(&ipf->ipf_lock);
         } else {
             dp_packet_batch_refill(pb, pkt, pb_idx);
         }

Fixed code:             } else {
                dp_packet_delete(pkt);