[102/105] ext4: fix a double free in ext4_register_li_request

From: Greg KH
Date: Tue Apr 12 2011 - 10:39:40 EST

2.6.38-stable review patch. If anyone has any objections, please let us know.


From: Tao Ma <boyu.mt@xxxxxxxxxx>

commit 46e4690bbd9a4f8d9e7c4f34e34b48f703ad47e0 upstream.

In ext4_register_li_request, we malloc a ext4_li_request and
inserts it into ext4_li_info->li_request_list. In case of any
error later, we free it in the end. But if we have some error
in ext4_run_lazyinit_thread, the whole li_request_list will be
dropped and freed in it. So we will double free this ext4_li_request.

This patch just sets elr to NULL after it is inserted to the list
so that the latter kfree won't double free it.

Signed-off-by: Tao Ma <boyu.mt@xxxxxxxxxx>
Reviewed-by: Lukas Czerner <lczerner@xxxxxxxxxx>
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

fs/ext4/super.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2978,6 +2978,12 @@ static int ext4_register_li_request(stru

sbi->s_li_request = elr;
+ /*
+ * set elr to NULL here since it has been inserted to
+ * the request_list and the removal and free of it is
+ * handled by ext4_clear_request_list from now on.
+ */
+ elr = NULL;

if (!(ext4_li_info->li_state & EXT4_LAZYINIT_RUNNING)) {
ret = ext4_run_lazyinit_thread();

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