sysctl: Fix data races in proc_dointvec_minmax().

A sysctl variable is accessed concurrently, and there is always a chance
of data-race.  So, all readers and writers need some basic protection to
avoid load/store-tearing.

This patch changes proc_dointvec_minmax() to use READ_ONCE() and
WRITE_ONCE() internally to fix data-races on the sysctl side.  For now,
proc_dointvec_minmax() itself is tolerant to a data-race, but we still
need to add annotations on the other subsystem's side.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2ab8c2a37e8f759e6bcce3ba3188ccd330714e5e..4d87832367f2046143aa579c0f6082323a44edf8 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -857,7 +857,7 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
                if ((param->min && *param->min > tmp) ||
                    (param->max && *param->max < tmp))
                        return -EINVAL;
-               *valp = tmp;
+               WRITE_ONCE(*valp, tmp);
        }
 
        return 0;