From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Wed, 6 Jul 2022 23:39:54 +0000 (-0700)
Subject: sysctl: Fix data races in proc_dointvec_minmax().
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=32d7f8da824407889eafc07b0c8ee7920648b571;p=linux.git

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 b152e0a30a2b9..f5134435fb9c0 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;