bsdacct: use del_timer_sync() in acct_exit_ns()

acct_exit_ns --> acct_file_reopen deletes timer without check timer
execution on other CPUs.  So acct_timeout() can change an unmapped memory.

Signed-off-by: Vitaliy Gusev <vgusev@openvz.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index 24f8c81fc48d..e4c0e1fee9b0 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -353,17 +353,18 @@ restart:
 
 void acct_exit_ns(struct pid_namespace *ns)
 {
-        struct bsd_acct_struct *acct;
+        struct bsd_acct_struct *acct = ns->bacct;
 
-        spin_lock(&acct_lock);
-        acct = ns->bacct;
-        if (acct != NULL) {
-                if (acct->file != NULL)
-                        acct_file_reopen(acct, NULL, NULL);
+        if (acct == NULL)
+                return;
 
-                kfree(acct);
-        }
+        del_timer_sync(&acct->timer);
+        spin_lock(&acct_lock);
+        if (acct->file != NULL)
+                acct_file_reopen(acct, NULL, NULL);
         spin_unlock(&acct_lock);
+
+        kfree(acct);
 }
 
 /*