sysctl: Fix data races in proc_dointvec_minmax().

[ Upstream commit f613d86d014b6375a4085901de39406598121e35 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 30681afbdb70ac8a220914711efb1a23ae1b1347..1800907da60cc0decd804c03972e5f91d0ab71c6 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -959,7 +959,7 @@ 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;