[Qemu-devel] [PATCH 1/4] linux-user/elfload.c: Avoid calling g_free() on uninitialized data

[Peter Maydell <peter.maydell@linaro.org>]

Avoid calling g_free() on unintialized data in the error-handling
paths in elf_core_dump() by splitting the initialization of the
elf_note_info struct out of fill_note_info() so that it's always
valid to call free_note_info() whether we got to the point of
being able to fill_note_info() or not.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 linux-user/elfload.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 5902f16..c0687e3 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2636,6 +2636,16 @@ static void fill_thread_info(struct elf_note_info *info, const CPUArchState *env
     info->notes_size += note_size(&ets->notes[0]);
 }
 
+static void init_note_info(struct elf_note_info *info)
+{
+    /* Initialize the elf_note_info structure so that it is at
+     * least safe to call free_note_info() on it. Must be
+     * called before calling fill_note_info().
+     */
+    memset(info, 0, sizeof (*info));
+    QTAILQ_INIT(&info->thread_list);
+}
+
 static int fill_note_info(struct elf_note_info *info,
                           long signr, const CPUArchState *env)
 {
@@ -2644,10 +2654,6 @@ static int fill_note_info(struct elf_note_info *info,
     TaskState *ts = (TaskState *)env->opaque;
     int i;
 
-    (void) memset(info, 0, sizeof (*info));
-
-    QTAILQ_INIT(&info->thread_list);
-
     info->notes = g_malloc0(NUMNOTES * sizeof (struct memelfnote));
     if (info->notes == NULL)
         return (-ENOMEM);
@@ -2781,6 +2787,8 @@ static int elf_core_dump(int signr, const CPUArchState *env)
     int segs = 0;
     int fd = -1;
 
+    init_note_info(&info);
+
     errno = 0;
     getrlimit(RLIMIT_CORE, &dumpsize);
     if (dumpsize.rlim_cur == 0)
-- 
1.8.5