[PATCH] Handle access of a target that has been removed

[Lee Duncan <lduncan@suse.com>]

Hello:

I recently got a report of a tgtd core dump from our opencloud
group. The stack trace showed that a strcmp against a NULL was causing
the failure:

----------------------------------------------------------------
Program terminated with signal 11, Segmentation fault.
(gdb) bt
#0  0x00007fa701817576 in __strcmp_sse42 () from /lib64/libc.so.6
#1  0x0000000000408012 in target_find_by_name (
    name=0x6ac16f "iqn.2010-10.org.openstack:volume-e812c705-80bc-4064-a84c-5559cda8b1ca") at iscsi/target.c:216
#2  0x0000000000406042 in login_start (conn=0x6abea8) at iscsi/iscsid.c:478
#3  0x0000000000406e77 in cmnd_exec_login (conn=<optimized out>)
    at iscsi/iscsid.c:654
#4  cmnd_execute (conn=<optimized out>) at iscsi/iscsid.c:914
#5  iscsi_rx_handler (conn=0x6abea8) at iscsi/iscsid.c:2064
#6  0x0000000000409e98 in iscsi_tcp_event_handler (fd=<optimized out>, 
    events=1, data=0x63a480 <target_list>) at iscsi/iscsi_tcp.c:158
#7  0x0000000000418f1e in event_loop () at tgtd.c:272
#8  0x0000000000419405 in main (argc=1, argv=<optimized out>) at tgtd.c:438
----------------------------------------------------------------

It looks like target_find_by_name() uses tgt_targetname(), but doesn't
account for the fact that it can return a NULL when the target being
looked up does not (now) exist:

----------------------------------------------------------------
char *tgt_targetname(int tid)            
{               
        struct target *target;      
                        
        target = target_lookup(tid);
        if (!target)
                return NULL;
        
        return target->name;
}                                   
----------------------------------------------------------------

I propose the following patch to address this:

--- 
diff --git a/usr/iscsi/target.c b/usr/iscsi/target.c
index 7afd7fd0ba87..b0a36e7de7b4 100644
--- a/usr/iscsi/target.c
+++ b/usr/iscsi/target.c
@@ -369,9 +369,11 @@ void target_list_build(struct iscsi_connection *conn, char *addr, char *name)
 struct iscsi_target *target_find_by_name(const char *name)
 {
        struct iscsi_target *target;
+       char *tname;
 
        list_for_each_entry(target, &iscsi_targets_list, tlist) {
-               if (!strcmp(tgt_targetname(target->tid), name))
+               tname = tgt_targetname(target->tid);
+               if (tname && !strcmp(tname, name))
                        return target;
        }
 

-- 
Lee Duncan