panic inducing use of gwlist_extract_first in dlr_pgsql.c

Hi All,

I'm finding what I think is incorrect use of gwlist_extract_first in the
postgres dlr implementations (it may also exist in others - I've not
checked yet). The DLR methods issue 'error's when they fail to return
results, etc but subsequent calls to gwlist_extract_first on NULL lists
cause 'panic's.

What I'm testing is the situation when the DLR DB is available on
start-up (we panic if it is not). If during during normal operation the
database is shutdown or temporarily unavailable (network issue, etc).
The select fail is an error but results in a panic.

2011-08-10 16:37:43 [18552] [3] ERROR: PGSQL: SELECT count(*) FROM
"dlr";
2011-08-10 16:37:43 [18552] [3] ERROR: PGSQL: FATAL:  terminating
connection due to administrator command
server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.

2011-08-10 16:37:43 [18552] [3] ERROR: PGSQL: Select failed!
2011-08-10 16:37:43 [18552] [3] ERROR: PGSQL: Could not get count of DLR
table
2011-08-10 16:37:43 [18552] [3] PANIC: gwlib/list.c:309:
gwlist_extract_first: Assertion `list != NULL' failed.
2011-08-10 16:37:43 [18552] [3] PANIC: /usr/sbin/bearerbox(gw_panic
+0x14b) [0x48b55b]
2011-08-10 16:37:43 [18552] [3]
PANIC: /usr/sbin/bearerbox(gwlist_extract_first+0x94) [0x489874]
2011-08-10 16:37:43 [18552] [3] PANIC: /usr/sbin/bearerbox [0x41e3d3]
2011-08-10 16:37:43 [18552] [3]
PANIC: /usr/sbin/bearerbox(bb_print_status+0x11d) [0x40edfd]
2011-08-10 16:37:43 [18552] [3] PANIC: /usr/sbin/bearerbox [0x415075]
2011-08-10 16:37:43 [18552] [3] PANIC: /usr/sbin/bearerbox [0x4823cf]
2011-08-10 16:37:43 [18552] [3] PANIC: /lib/libpthread.so.0
[0x2b0e670a9fc7]
2011-08-10 16:37:43 [18552] [3] PANIC: /lib/libc.so.6(clone+0x6d)
[0x2b0e67a8664d]

The attached patch addresses this (for postgres implementation only - I
can check the others if required). Once applied The result on the status
page is ..

DLR: -1 queued, using pgsql storage

And when a DLR is received ...

2011-08-10 16:44:53 [18889] [11] ERROR: PGSQL: FATAL:  terminating
connection due to administrator command
server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.

2011-08-10 16:44:53 [18889] [11] ERROR: PGSQL: Select failed!
2011-08-10 16:44:53 [18889] [11] DEBUG: no rows found
2011-08-10 16:44:53 [18889] [11] WARNING: DLR[pgsql]: DLR from SMSC<FOO>
for DST<02xxxxxxxxx> not found.
2011-08-10 16:44:53 [18889] [11] ERROR: SMPP[FOO]: got DLR but could not
find message or was not interested in it id<534001841355>
dst<02xxxxxxxxx>, type<1>

Cheers,
Alan

Index: gw/dlr_pgsql.c
===================================================================
--- gw/dlr_pgsql.c	(revision 4916)
+++ gw/dlr_pgsql.c	(working copy)
@@ -185,7 +185,7 @@
 
     if (result == NULL || gwlist_len(result) < 1) {
         debug("dlr.pgsql", 0, "no rows found");
-        while((row = gwlist_extract_first(result)))
+        while(result && (row = gwlist_extract_first(result)) != NULL)
             gwlist_destroy(row, octstr_destroy_item);
         gwlist_destroy(result, NULL);
         return NULL;
@@ -282,7 +282,8 @@
         ret = atol(octstr_get_cstr(gwlist_get(gwlist_get(res, 0), 0)));
     }
 
-    gwlist_destroy(gwlist_extract_first(res), octstr_destroy_item);
+    if ( res != NULL ) 
+      gwlist_destroy(gwlist_extract_first(res), octstr_destroy_item);
     gwlist_destroy(res, NULL);
         
     return ret;