zebra: fix table heap-after-free crash

Fix a heap-after-free that causes zebra to crash even without
address-sanitizer. To reproduce:

> echo "100 my_table" | tee -a /etc/iproute2/rt_tables
> ip route add blackhole default table 100
> ip route show table 100
> ip l add red type vrf table 100
> ip l del red
> ip route del blackhole default table 100

> ==2866266==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000154f54 at pc 0x7fa32474b83f bp 0x7ffe94f67d90 sp 0x7ffe94f67d88
> READ of size 1 at 0x606000154f54 thread T0
>     #0 0x7fa32474b83e in rn_hash_node_const_find lib/table.c:28
>     #1 0x7fa32474bab1 in rn_hash_node_find lib/table.c:28
>     #2 0x7fa32474d783 in route_node_get lib/table.c:283
>     #3 0x7fa3247328dd in srcdest_rnode_get lib/srcdest_table.c:231
>     #4 0x55b0e4fa8da4 in rib_find_rn_from_ctx zebra/zebra_rib.c:1957
>     #5 0x55b0e4fa8e31 in rib_process_result zebra/zebra_rib.c:1988
>     #6 0x55b0e4fb9d64 in rib_process_dplane_results zebra/zebra_rib.c:4894
>     #7 0x7fa32476689c in event_call lib/event.c:1996
>     #8 0x7fa32463b7b2 in frr_run lib/libfrr.c:1232
>     #9 0x55b0e4e6c32a in main zebra/main.c:526
>     #10 0x7fa32424fd09 in __libc_start_main ../csu/libc-start.c:308
>     #11 0x55b0e4e2d649 in _start (/usr/lib/frr/zebra+0x1a1649)
>
> 0x606000154f54 is located 20 bytes inside of 56-byte region [0x606000154f40,0x606000154f78)
> freed by thread T0 here:
>     #0 0x7fa324ca9b6f in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:123
>     #1 0x7fa324668d8f in qfree lib/memory.c:130
>     #2 0x7fa32474c421 in route_table_free lib/table.c:126
>     #3 0x7fa32474bf96 in route_table_finish lib/table.c:46
>     #4 0x55b0e4fbca3a in zebra_router_free_table zebra/zebra_router.c:191
>     #5 0x55b0e4fbccea in zebra_router_release_table zebra/zebra_router.c:214
>     #6 0x55b0e4fd428e in zebra_vrf_disable zebra/zebra_vrf.c:219
>     #7 0x7fa32476fabf in vrf_disable lib/vrf.c:326
>     #8 0x7fa32476f5d4 in vrf_delete lib/vrf.c:231
>     #9 0x55b0e4e4ad36 in interface_vrf_change zebra/interface.c:1478
>     #10 0x55b0e4e4d5d2 in zebra_if_dplane_ifp_handling zebra/interface.c:1949
>     #11 0x55b0e4e4fb89 in zebra_if_dplane_result zebra/interface.c:2268
>     #12 0x55b0e4fb9f26 in rib_process_dplane_results zebra/zebra_rib.c:4954
>     #13 0x7fa32476689c in event_call lib/event.c:1996
>     #14 0x7fa32463b7b2 in frr_run lib/libfrr.c:1232
>     #15 0x55b0e4e6c32a in main zebra/main.c:526
>     #16 0x7fa32424fd09 in __libc_start_main ../csu/libc-start.c:308
>
> previously allocated by thread T0 here:
>     #0 0x7fa324caa037 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
>     #1 0x7fa324668c4d in qcalloc lib/memory.c:105
>     #2 0x7fa32474bf33 in route_table_init_with_delegate lib/table.c:38
>     #3 0x7fa32474e73c in route_table_init lib/table.c:512
>     #4 0x55b0e4fbc353 in zebra_router_get_table zebra/zebra_router.c:137
>     #5 0x55b0e4fd4da0 in zebra_vrf_table_create zebra/zebra_vrf.c:358
>     #6 0x55b0e4fd3d30 in zebra_vrf_enable zebra/zebra_vrf.c:140
>     #7 0x7fa32476f9b2 in vrf_enable lib/vrf.c:286
>     #8 0x55b0e4e4af76 in interface_vrf_change zebra/interface.c:1533
>     #9 0x55b0e4e4d612 in zebra_if_dplane_ifp_handling zebra/interface.c:1968
>     #10 0x55b0e4e4fb89 in zebra_if_dplane_result zebra/interface.c:2268
>     #11 0x55b0e4fb9f26 in rib_process_dplane_results zebra/zebra_rib.c:4954
>     #12 0x7fa32476689c in event_call lib/event.c:1996
>     #13 0x7fa32463b7b2 in frr_run lib/libfrr.c:1232
>     #14 0x55b0e4e6c32a in main zebra/main.c:526
>     #15 0x7fa32424fd09 in __libc_start_main ../csu/libc-start.c:308

Linux RT table can be created before it is assigned and remains after it
is unassigned.

Do not release the table at VRF disabling but change the owner to the
default VRF. At VRF enabling, change the table owner to the VRF.

Fixes: d8612e6 ("zebra: Track tables allocated by vrf and cleanup")
Signed-off-by: Louis Scalbert <[email protected]>

zebra/zebra_vrf.c

@@ -158,6 +158,8 @@ static int zebra_vrf_enable(struct vrf *vrf)
 static int zebra_vrf_disable(struct vrf *vrf)
 {
 	struct zebra_vrf *zvrf = vrf->info;
+	struct zebra_vrf *zvrf_default = vrf_info_lookup(VRF_DEFAULT);
+	struct rib_table_info *info;
 	struct interface *ifp;
 	afi_t afi;
 	safi_t safi;
@@ -216,8 +218,12 @@ static int zebra_vrf_disable(struct vrf *vrf)
 		 * we no-longer need this pointer.
 		 */
 		for (safi = SAFI_UNICAST; safi <= SAFI_MULTICAST; safi++) {
-			zebra_router_release_table(zvrf, zvrf->table_id, afi,
-						   safi);
+			if (!zvrf->table[afi][safi])
+				continue;
+
+			info = route_table_get_info(zvrf->table[afi][safi]);
+			info->zvrf = zvrf_default;
+
 			zvrf->table[afi][safi] = NULL;
 		}
 	}
@@ -349,6 +355,7 @@ static void zebra_rnhtable_node_cleanup(struct route_table *table,
 static void zebra_vrf_table_create(struct zebra_vrf *zvrf, afi_t afi,
 				   safi_t safi)
 {
+	struct rib_table_info *info;
 	struct route_node *rn;
 	struct prefix p;
 
@@ -357,6 +364,9 @@ static void zebra_vrf_table_create(struct zebra_vrf *zvrf, afi_t afi,
 	zvrf->table[afi][safi] =
 		zebra_router_get_table(zvrf, zvrf->table_id, afi, safi);
 
+	info = route_table_get_info(zvrf->table[afi][safi]);
+	info->zvrf = zvrf;
+
 	memset(&p, 0, sizeof(p));
 	p.family = afi2family(afi);