isisd: fix heap-after-free with prefix sid

> ==2334217==ERROR: AddressSanitizer: heap-use-after-free on address 0x61000001d0a0 at pc 0x563828c8de6f bp 0x7fffbdaee560 sp 0x7fffbdaee558
> READ of size 1 at 0x61000001d0a0 thread T0
>     #0 0x563828c8de6e in prefix_sid_cmp isisd/isis_spf.c:187
>     #1 0x7f84b8204f71 in hash_get lib/hash.c:142
>     #2 0x7f84b82055ec in hash_lookup lib/hash.c:184
>     #3 0x563828c8e185 in isis_spf_prefix_sid_lookup isisd/isis_spf.c:209
>     #4 0x563828c90642 in isis_spf_add2tent isisd/isis_spf.c:598
>     #5 0x563828c91cd0 in process_N isisd/isis_spf.c:824
>     #6 0x563828c93852 in isis_spf_process_lsp isisd/isis_spf.c:1041
>     #7 0x563828c98dde in isis_spf_loop isisd/isis_spf.c:1821
>     #8 0x563828c998de in isis_run_spf isisd/isis_spf.c:1983
>     #9 0x563828c99c7b in isis_run_spf_with_protection isisd/isis_spf.c:2009
>     #10 0x563828c9a60d in isis_run_spf_cb isisd/isis_spf.c:2090
>     #11 0x7f84b835c72d in event_call lib/event.c:2011
>     #12 0x7f84b8236d93 in frr_run lib/libfrr.c:1217
>     #13 0x563828c21918 in main isisd/isis_main.c:346
>     #14 0x7f84b7e4fd09 in __libc_start_main ../csu/libc-start.c:308
>     #15 0x563828c20df9 in _start (/usr/lib/frr/isisd+0xf5df9)
>
> 0x61000001d0a0 is located 96 bytes inside of 184-byte region [0x61000001d040,0x61000001d0f8)
> freed by thread T0 here:
>     #0 0x7f84b88a9b6f in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:123
>     #1 0x7f84b8263bae in qfree lib/memory.c:130
>     #2 0x563828c8e433 in isis_vertex_del isisd/isis_spf.c:249
>     #3 0x563828c91c95 in process_N isisd/isis_spf.c:811
>     #4 0x563828c93852 in isis_spf_process_lsp isisd/isis_spf.c:1041
>     #5 0x563828c98dde in isis_spf_loop isisd/isis_spf.c:1821
>     #6 0x563828c998de in isis_run_spf isisd/isis_spf.c:1983
>     #7 0x563828c99c7b in isis_run_spf_with_protection isisd/isis_spf.c:2009
>     #8 0x563828c9a60d in isis_run_spf_cb isisd/isis_spf.c:2090
>     #9 0x7f84b835c72d in event_call lib/event.c:2011
>     #10 0x7f84b8236d93 in frr_run lib/libfrr.c:1217
>     #11 0x563828c21918 in main isisd/isis_main.c:346
>     #12 0x7f84b7e4fd09 in __libc_start_main ../csu/libc-start.c:308
>
> previously allocated by thread T0 here:
>     #0 0x7f84b88aa037 in __interceptor_calloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:154
>     #1 0x7f84b8263a6c in qcalloc lib/memory.c:105
>     #2 0x563828c8e262 in isis_vertex_new isisd/isis_spf.c:225
>     #3 0x563828c904db in isis_spf_add2tent isisd/isis_spf.c:588
>     #4 0x563828c91cd0 in process_N isisd/isis_spf.c:824
>     #5 0x563828c93852 in isis_spf_process_lsp isisd/isis_spf.c:1041
>     #6 0x563828c98dde in isis_spf_loop isisd/isis_spf.c:1821
>     #7 0x563828c998de in isis_run_spf isisd/isis_spf.c:1983
>     #8 0x563828c99c7b in isis_run_spf_with_protection isisd/isis_spf.c:2009
>     #9 0x563828c9a60d in isis_run_spf_cb isisd/isis_spf.c:2090
>     #10 0x7f84b835c72d in event_call lib/event.c:2011
>     #11 0x7f84b8236d93 in frr_run lib/libfrr.c:1217
>     #12 0x563828c21918 in main isisd/isis_main.c:346
>     #13 0x7f84b7e4fd09 in __libc_start_main ../csu/libc-start.c:308
>
> SUMMARY: AddressSanitizer: heap-use-after-free isisd/isis_spf.c:187 in prefix_sid_cmp
> Shadow bytes around the buggy address:
>   0x0c207fffb9c0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
>   0x0c207fffb9d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa
>   0x0c207fffb9e0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
>   0x0c207fffb9f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa
>   0x0c207fffba00: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
> =>0x0c207fffba10: fd fd fd fd[fd]fd fd fd fd fd fd fd fd fd fd fa
>   0x0c207fffba20: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
>   0x0c207fffba30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa
>   0x0c207fffba40: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
>   0x0c207fffba50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa
>   0x0c207fffba60: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> Shadow byte legend (one shadow byte represents 8 application bytes):
>   Addressable:           00
>   Partially addressable: 01 02 03 04 05 06 07
>   Heap left redzone:       fa
>   Freed heap region:       fd
>   Stack left redzone:      f1
>   Stack mid redzone:       f2
>   Stack right redzone:     f3
>   Stack after return:      f5
>   Stack use after scope:   f8
>   Global redzone:          f9
>   Global init order:       f6
>   Poisoned by user:        f7
>   Container overflow:      fc
>   Array cookie:            ac
>   Intra object redzone:    bb
>   ASan internal:           fe
>   Left alloca redzone:     ca
>   Right alloca redzone:    cb
>   Shadow gap:              cc
> ==2334217==ABORTING

Fixes: 2f7cc7b ("isisd: detect Prefix-SID collisions and handle them appropriately")
Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>

isisd/isis_spf.c

@@ -703,6 +703,7 @@ static void isis_spf_add_local(struct isis_spftree *spftree,
 		} else { /* vertex->d_N > cost */
 			/*         f) */
 			isis_vertex_queue_delete(&spftree->tents, vertex);
+			hash_release(spftree->prefix_sids, vertex);
 			isis_vertex_del(vertex);
 		}
 	}
@@ -808,6 +809,7 @@ static void process_N(struct isis_spftree *spftree, enum vertextype vtype,
 			/*      4) */
 		} else {
 			isis_vertex_queue_delete(&spftree->tents, vertex);
+			hash_release(spftree->prefix_sids, vertex);
 			isis_vertex_del(vertex);
 		}
 	}