From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Wed, 6 Jul 2022 23:39:55 +0000 (-0700)
Subject: sysctl: Fix data races in proc_douintvec_minmax().
X-Git-Tag: v5.10.132~68
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=e3a2144b3b6bf9ecafd91087c8b8b48171ec19df;p=users%2Fdwmw2%2Flinux.git

sysctl: Fix data races in proc_douintvec_minmax().

[ Upstream commit 2d3b559df3ed39258737789aae2ae7973d205bc1 ]

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

Fixes: 61d9b56a8920 ("sysctl: add unsigned int range support")
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 1800907da60cc..df6090ba1d0b9 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1025,7 +1025,7 @@ static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
 		    (param->max && *param->max < tmp))
 			return -ERANGE;
 
-		*valp = tmp;
+		WRITE_ONCE(*valp, tmp);
 	}
 
 	return 0;