[PATCH 5.15 051/167] sysctl: Fix data races in proc_dointvec().

Greg Kroah-Hartman
2022-07-19T12:36:55Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 1f1be04b4d48a2475ea1aab46a99221bfc5c0968 ]

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() to use READ_ONCE() and WRITE_ONCE()
internally to fix data-races on the sysctl side. For now, proc_dointvec()
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 | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 0586047f7323..11f0714273ab 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -566,14 +566,14 @@ static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
if (*negp) {
if (*lvalp > (unsigned long) INT_MAX + 1)
return -EINVAL;
- *valp = -*lvalp;
+ WRITE_ONCE(*valp, -*lvalp);
} else {
if (*lvalp > (unsigned long) INT_MAX)
return -EINVAL;
- *valp = *lvalp;
+ WRITE_ONCE(*valp, *lvalp);
}
} else {
- int val = *valp;
+ int val = READ_ONCE(*valp);
if (val < 0) {
*negp = true;
*lvalp = -(unsigned long)val;
--
2.35.1