sysctl: Fix data-races in proc_dointvec_ms_jiffies().

stable inclusion
from stable-v5.10.132
commit b8871d9186029458786f62e8f8ef72543ea274ac
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YS3T

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b8871d9186029458786f62e8f8ef72543ea274ac

--------------------------------

[ Upstream commit 7d1025e5 ]

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

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: NKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

kernel/sysctl.c

@@ -1334,9 +1334,9 @@ static int do_proc_dointvec_ms_jiffies_conv(bool *negp, unsigned long *lvalp,
 
 		if (jif > INT_MAX)
 			return 1;
-		*valp = (int)jif;
+		WRITE_ONCE(*valp, (int)jif);
 	} else {
-		int val = *valp;
+		int val = READ_ONCE(*valp);
 		unsigned long lval;
 		if (val < 0) {
 			*negp = true;
@@ -1404,8 +1404,8 @@ int proc_dointvec_userhz_jiffies(struct ctl_table *table, int write,
  * @ppos: the current position in the file
  *
  * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
- * values from/to the user buffer, treated as an ASCII string. 
- * The values read are assumed to be in 1/1000 seconds, and 
+ * values from/to the user buffer, treated as an ASCII string.
+ * The values read are assumed to be in 1/1000 seconds, and
  * are converted into jiffies.
  *
  * Returns 0 on success.