[PATCH]dm_get_map: fix segfault when can't found target

[Wu Guanghao <wuguanghao3@xxxxxxxxxx>]

We got a segfault when we test multipath + iscsi.

(gdb) bt
#0  __strlen_avx2 () at ../sysdeps/x86_64/multiarch/strlen-avx2.S:74
#1  0x00007f694306cd23 in __GI___strdup (s=0x0) at strdup.c:41
#2  0x00007f69433a147c in dm_get_map (name=0x55d4bc090320 "3600140537cde137ea8c43d8a971462c7",
    size=size@entry=0x55d4bc0270d8, outparams=outparams@entry=0x7f6941add640) at devmapper.c:688
#3  0x00007f69433cbbdf in update_multipath_table (mpp=mpp@entry=0x55d4bc026f30,
    pathvec=pathvec@entry=0x55d4bc063990, flags=flags@entry=0) at structs_vec.c:426
#4  0x00007f69433cbfe5 in update_multipath_strings (mpp=0x55d4bc026f30, pathvec=0x55d4bc063990)
    at structs_vec.c:526
#5  0x000055d4bb52e03e in check_path (vecs=0x55d4bbfad760, pp=0x7f692402d270, ticks=<optimized out>)
    at main.c:2280
#6  0x000055d4bb52f3e2 in checkerloop (ap=0x55d4bbfad760) at main.c:2542
#7  0x00007f694305b3ba in start_thread (arg=<optimized out>) at pthread_create.c:443
#8  0x00007f69430ddb40 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
(gdb) f 2
#2  0x00007f69433a147c in dm_get_map (name=0x55d4bc090320 "3600140537cde137ea8c43d8a971462c7",
    size=size@entry=0x55d4bc0270d8, outparams=outparams@entry=0x7f6941add640) at devmapper.c:688
688			*outparams = strdup(params);
(gdb) l
683			*size = length;
684	
685		if (!outparams)
686			r = DMP_OK;
687		else {
688			*outparams = strdup(params);
689			r = *outparams ? DMP_OK : DMP_ERR;
690		}
691	
692	out:
(gdb) p params
$1 = 0x0

If can't found target, we should goto out

Signed-off-by: Wu Guanghao <wuguanghao3@xxxxxxxxxx>
---
 libmultipath/devmapper.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
index 2507f77f..450b17ef 100644
--- a/libmultipath/devmapper.c
+++ b/libmultipath/devmapper.c
@@ -682,8 +682,8 @@ int dm_get_map(const char *name, unsigned long long *size, char **outparams)
        r = DMP_NOT_FOUND;
        /* Fetch 1st target */
        if (dm_get_next_target(dmt, NULL, &start, &length,
-                              &target_type, &params) != NULL)
-               /* more than one target */
+                              &target_type, &params) != NULL || !params)
+               /* more than one target or not found target */
                goto out;

        if (size)
--
2.27.0

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