From: wei huang <[email protected]>

Problem:
Multipathd segment faulty occured when device policy was configured in 
multipath.conf as follow:
#This is a device configuration just for COMPELNT device
devices {
       device {
               vendor                  COMPELNT
               dev_loss_tmo            120
               scheduler               deadline
       }
}

The call trace is:
Program received signal SIGSEGV, Segmentation fault.
0x00007f4eaaf49251 in __strstr_sse2 () from /lib64/libc.so.6
(gdb) bt
#0  0x00007f4eaaf49251 in __strstr_sse2 () from /lib64/libc.so.6
#1  0x00007f4eabba879c in add_feature (f=f@entry=0x211b248, 
n=n@entry=0x7f4eabbc530a queue_if_no_path)
    at structs.c:524
#2  0x00007f4eabba6993 in merge_hwe (src=0x2148c70, dst=0x211b220) at 
config.c:359
#3  factorize_hwtable (hw=0x214b800, n=n@entry=77) at config.c:452
#4  0x00007f4eabba7850 in load_config (file=file@entry=0x4144c8 
/etc/multipath.conf) at config.c:651
#5  0x0000000000408959 in reconfigure (vecs=vecs@entry=0x2128ae0) at main.c:2078
#6  0x00000000004063c6 in child (param=0x0) at main.c:2483
#7  main (argc=<optimized out>, argv=<optimized out>) at main.c:2725
(gdb) up
#1  0x00007f4eabba879c in add_feature (f=f@entry=0x211b248, 
n=n@entry=0x7f4eabbc530a queue_if_no_path)
    at structs.c:524
524             if (strstr(*f, n))
(gdb) p *f
 = 0x0

Reasons:
When multipathd loads config, it will call merge_hwe() to merge the features 
between default_hw[] and config.
If the vender is not configured features in default_hw[], dst->features's value 
will be null. So strstr()'s first
parameter *f is null in add_feature(),too.

Signed-off-by: wei huang <[email protected]>
---
 libmultipath/structs.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/libmultipath/structs.c b/libmultipath/structs.c
index fee58e5..f673325 100644
--- a/libmultipath/structs.c
+++ b/libmultipath/structs.c
@@ -520,6 +520,17 @@ add_feature (char **f, char *n)
        if (!n || *n == '0')
                return 0;
 
+       /* default feature is null */
+       if(!*f)
+       {
+               l = asprintf(&t, "1 %s", n);
+               if(l == -1)
+                       return 1;
+                       
+               *f = t;
+               return 0;
+       }
+
        /* Check if feature is already present */
        if (strstr(*f, n))
                return 0;
-- 
2.8.1.windows.1

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