memcg: res_counter_read_u64(): fix potential races on 32-bit machines

res_counter_read_u64 reads u64 value without lock.  It's dangerous in a
32bit environment.  Add locking.

Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: Greg Thelen <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Minchan Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/kernel/res_counter.c b/kernel/res_counter.c
index c7eaa37a768b785cf69cd2eb64ab3fb75c052124..34683efa2cceee37f0a76db7531b8f5fc265a325 100644 (file)
--- a/kernel/res_counter.c
+++ b/kernel/res_counter.c
@@ -126,10 +126,24 @@ ssize_t res_counter_read(struct res_counter *counter, int member,
                        pos, buf, s - buf);
 }
 
+#if BITS_PER_LONG == 32
+u64 res_counter_read_u64(struct res_counter *counter, int member)
+{
+       unsigned long flags;
+       u64 ret;
+
+       spin_lock_irqsave(&counter->lock, flags);
+       ret = *res_counter_member(counter, member);
+       spin_unlock_irqrestore(&counter->lock, flags);
+
+       return ret;
+}
+#else
 u64 res_counter_read_u64(struct res_counter *counter, int member)
 {
        return *res_counter_member(counter, member);
 }
+#endif
 
 int res_counter_memparse_write_strategy(const char *buf,
                                        unsigned long long *res)