[PATCH] tools: fix NULL_AFTER_DEREF in image-host.c

[Anton Moryakov]

Report of the static analyzer:
1. NULL_AFTER_DEREF Pointer 'str', which is dereferenced at image-host.c:688 by 
calling function 'strdup', is compared to a NULL value at image-host.c:691.
2. NULL_AFTER_DEREF Pointer 'list', which is dereferenced at image-host.c:689, 
is compared to a NULL value at image-host.c:691.

Corrections explained:
1. Checking for NULL before using pointers: The if (!list || !str) check is now 
performed before calling strdup and realloc, which prevents null pointer 
dereferences.
2. Checking the result of strdup: strdup can return NULL if memory allocation 
fails. This also needs to be checked.
3. Checking the result of realloc: If realloc returns NULL, then memory has not 
been allocated and dup must be freed to avoid memory leaks.

Triggers found by static analyzer Svace.

Signed-off-by: Anton Moryakov <ant.v.moryakov at gmail.com>

---
 tools/image-host.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/tools/image-host.c b/tools/image-host.c
index 84095d760c..821c8db616 100644
--- a/tools/image-host.c
+++ b/tools/image-host.c
@@ -716,11 +716,21 @@ static int strlist_add(struct strlist *list, const char 
*str)
 {
        char *dup;
 
+       if (!list || !str)
+               return -1;
+
        dup = strdup(str);
+       if(!dup)
+               return -1;
+
        list->strings = realloc(list->strings,
                                (list->count + 1) * sizeof(char *));
-       if (!list || !str)
-               return -1;
+       if (!list->strings)
+    {
+        free(dup);  
+        return -1;
+    }
+       
        list->strings[list->count++] = dup;
 
        return 0;
-- 
2.30.2