ldpd: Prevent usage after free

error	26-Nov-2020 14:35:02	ERROR: AddressSanitizer: heap-use-after-free on address 0x631000024838 at pc 0x55cefae977e9 bp 0x7ffdd3546860 sp 0x7ffdd3546850
error	26-Nov-2020 14:35:02	READ of size 4 at 0x631000024838 thread T0
error	26-Nov-2020 14:35:02	    #0 0x55cefae977e8 in ldpe_imsg_compose_parent_sync ldpd/ldpe.c:256
error	26-Nov-2020 14:35:02	    #1 0x55cefae9ab13 in vlog ldpd/log.c:53
error	26-Nov-2020 14:35:02	    #2 0x55cefae9b21f in log_info ldpd/log.c:102
error	26-Nov-2020 14:35:02	    #3 0x55cefae96eae in ldpe_shutdown ldpd/ldpe.c:237
error	26-Nov-2020 14:35:02	    #4 0x55cefae99254 in ldpe_dispatch_main ldpd/ldpe.c:585
error	26-Nov-2020 14:35:02	    #5 0x55cefaf93875 in thread_call lib/thread.c:1681
error	26-Nov-2020 14:35:02	    #6 0x55cefae97304 in ldpe ldpd/ldpe.c:136
error	26-Nov-2020 14:35:02	    #7 0x55cefae5a2e2 in main ldpd/ldpd.c:322
error	26-Nov-2020 14:35:02	    #8 0x7f4ef0c33b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
error	26-Nov-2020 14:35:02	    #9 0x55cefae525e9 in _start (/usr/lib/frr/ldpd+0xb35e9)
error	26-Nov-2020 14:35:02
error	26-Nov-2020 14:35:02	0x631000024838 is located 65592 bytes inside of 65632-byte region [0x631000014800,0x631000024860)
error	26-Nov-2020 14:35:02	freed by thread T0 here:
error	26-Nov-2020 14:35:02	    #0 0x7f4ef21e37a8 in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xde7a8)
error	26-Nov-2020 14:35:02	    #1 0x55cefae96e91 in ldpe_shutdown ldpd/ldpe.c:234
error	26-Nov-2020 14:35:02	    #2 0x55cefae99254 in ldpe_dispatch_main ldpd/ldpe.c:585
error	26-Nov-2020 14:35:02	    #3 0x55cefaf93875 in thread_call lib/thread.c:1681
error	26-Nov-2020 14:35:02	    #4 0x55cefae97304 in ldpe ldpd/ldpe.c:136
error	26-Nov-2020 14:35:02	    #5 0x55cefae5a2e2 in main ldpd/ldpd.c:322
error	26-Nov-2020 14:35:02	    #6 0x7f4ef0c33b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
error	26-Nov-2020 14:35:02
error	26-Nov-2020 14:35:02	previously allocated by thread T0 here:
error	26-Nov-2020 14:35:02	    #0 0x7f4ef21e3d28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
error	26-Nov-2020 14:35:02	    #1 0x55cefae9725d in ldpe ldpd/ldpe.c:127
error	26-Nov-2020 14:35:02	    #2 0x55cefae5a2e2 in main ldpd/ldpd.c:322
error	26-Nov-2020 14:35:02	    #3 0x7f4ef0c33b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)

Clean this problem up in the same way as the previous commit

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

Author: donaldsharp

ldpd/ldpe.c

@@ -49,6 +49,7 @@ struct ldpd_conf	*leconf;
 struct ldpd_sysdep	 sysdep;
 #endif
 
+static struct imsgev    iev_main_data;
 static struct imsgev	*iev_main, *iev_main_sync;
 static struct imsgev	*iev_lde;
 #ifdef __OpenBSD__
@@ -124,8 +125,8 @@ ldpe(void)
 		        &iev_main->ev_read);
 	iev_main->handler_write = ldp_write_handler;
 
-	if ((iev_main_sync = calloc(1, sizeof(struct imsgev))) == NULL)
-		fatal(NULL);
+	memset(&iev_main_data, 0, sizeof(iev_main_data));
+	iev_main_sync = &iev_main_data;
 	imsg_init(&iev_main_sync->ibuf, LDPD_FD_SYNC);
 
 	/* create base configuration */
@@ -231,7 +232,6 @@ ldpe_shutdown(void)
 	if (iev_lde)
 		free(iev_lde);
 	free(iev_main);
-	free(iev_main_sync);
 	free(pkt_ptr);
 
 	log_info("ldp engine exiting");