[Qemu-devel] [PATCH 2/2] qemu queue: fix uninitialized removals

[Tim Hardeck <thardeck@suse.de>]

When calling QTAILQ_REMOVE or QLIST_REMOVE on an unitialized list
QEMU segfaults.

Check for this case specifically on item removal.

Signed-off-by: Tim Hardeck <thardeck@suse.de>
---
 qemu-queue.h |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/qemu-queue.h b/qemu-queue.h
index 9288cd8..47ed239 100644
--- a/qemu-queue.h
+++ b/qemu-queue.h
@@ -141,7 +141,9 @@ struct {                                                                \
         if ((elm)->field.le_next != NULL)                               \
                 (elm)->field.le_next->field.le_prev =                   \
                     (elm)->field.le_prev;                               \
-        *(elm)->field.le_prev = (elm)->field.le_next;                   \
+        if ((elm)->field.le_prev != NULL) {                             \
+            *(elm)->field.le_prev = (elm)->field.le_next;               \
+        }                                                               \
 } while (/*CONSTCOND*/0)
 
 #define QLIST_FOREACH(var, head, field)                                 \
@@ -381,7 +383,9 @@ struct {                                                                \
                     (elm)->field.tqe_prev;                              \
         else                                                            \
                 (head)->tqh_last = (elm)->field.tqe_prev;               \
-        *(elm)->field.tqe_prev = (elm)->field.tqe_next;                 \
+        if ((elm)->field.tqe_prev != NULL) {                            \
+            *(elm)->field.tqe_prev = (elm)->field.tqe_next;             \
+        }                                                               \
 } while (/*CONSTCOND*/0)
 
 #define QTAILQ_FOREACH(var, head, field)                                \
-- 
1.7.10.4