[PATCH 5.15 053/167] sysctl: Fix data races in proc_dointvec_minmax().

Greg Kroah-Hartman
2022-07-19T12:35:41Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ 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>
---
kernel/sysctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b152e0a30a2b..f5134435fb9c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -988,7 +988,7 @@ 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;
--
2.35.1