[git commit] insque: fix segfault on (prev == NULL)

[Bernhard Reutner-Fischer]

commit: http://git.uclibc.org/uClibc/commit/?id=f9ae36ebf1d8e300c77dfd16b55514ea5a96751f
branch: http://git.uclibc.org/uClibc/commit/?id=refs/heads/master

Since version 2.5 glibc allows prev to be a NULL pointer in insque, whereas
uClibc segfaults in this case. This fixes the issue and makes insque
initialize q_forw and q_back with NULLs if prev == NULL.

Signed-off-by: Bartosz Golaszewski <bartekgola at gmail.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop at gmail.com>
---
 libc/misc/search/insremque.c |   20 ++++++++++++++------
 1 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/libc/misc/search/insremque.c b/libc/misc/search/insremque.c
index c4a75ab..9939942 100644
--- a/libc/misc/search/insremque.c
+++ b/libc/misc/search/insremque.c
@@ -26,12 +26,20 @@
 void
 insque (void *elem, void *prev)
 {
-  struct qelem *next = ((struct qelem *) prev)->q_forw;
-  ((struct qelem *) prev)->q_forw = (struct qelem *) elem;
-  if (next != NULL)
-    next->q_back = (struct qelem *) elem;
-  ((struct qelem *) elem)->q_forw = next;
-  ((struct qelem *) elem)->q_back = (struct qelem *) prev;
+  if (prev == NULL)
+    {
+      ((struct qelem *) elem)->q_forw = NULL;
+      ((struct qelem *) elem)->q_back = NULL;
+    }
+  else
+    {
+      struct qelem *next = ((struct qelem *) prev)->q_forw;
+      ((struct qelem *) prev)->q_forw = (struct qelem *) elem;
+      if (next != NULL)
+        next->q_back = (struct qelem *) elem;
+      ((struct qelem *) elem)->q_forw = next;
+      ((struct qelem *) elem)->q_back = (struct qelem *) prev;
+    }
 }
 
 #endif