[PATCH] attrib-server: Allow zero length attribute update

attrib_db_update always fails when g_try_realloc returns NULL, not
taking into account that the length passed to g_try_realloc could be
zero. In this case, g_try_realloc frees the currently allocated memory
and returns NULL.
As a result, not only will attrib_db_update fail needlessly, a
use-after-free could occur as the attribute's length will still hold the
length of the freed buffer.

Fix this by only returning an error if the length is non-zero.
---
 src/attrib-server.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/attrib-server.c b/src/attrib-server.c
index 3291e2d..dd1bba4 100644
--- a/src/attrib-server.c
+++ b/src/attrib-server.c

@@ -1456,7 +1456,7 @@ int attrib_db_update(struct btd_adapter *adapter, uint16_t handle,
 	a = dl->data;
 
 	a->data = g_try_realloc(a->data, len);
-	if (a->data == NULL)
+	if (len && a->data == NULL)
 		return -ENOMEM;
 
 	a->len = len;

-- 
1.7.7.6