[PATCH 5.10 124/124] sysctl: Fix data-races in proc_dou8vec_minmax().

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>

commit 7dee5d7747a69aa2be41f04c6a7ecfe3ac8cdf18 upstream.

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_dou8vec_minmax() to use READ_ONCE() and
WRITE_ONCE() internally to fix data-races on the sysctl side.  For now,
proc_dou8vec_minmax() itself is tolerant to a data-race, but we still
need to add annotations on the other subsystem's side.

Fixes: cb9444130662 ("sysctl: add proc_dou8vec_minmax()")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/sysctl.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1109,13 +1109,13 @@ int proc_dou8vec_minmax(struct ctl_table
 
 	tmp.maxlen = sizeof(val);
 	tmp.data = &val;
-	val = *data;
+	val = READ_ONCE(*data);
 	res = do_proc_douintvec(&tmp, write, buffer, lenp, ppos,
 				do_proc_douintvec_minmax_conv, &param);
 	if (res)
 		return res;
 	if (write)
-		*data = val;
+		WRITE_ONCE(*data, val);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(proc_dou8vec_minmax);