[PATCH 5.10 043/112] sysctl: Fix data races in proc_douintvec().

Greg Kroah-Hartman
2022-07-19T12:18:57Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 4762b532ec9539755aab61445d5da6e1926ccb99 ]

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

Fixes: e7d316a02f68 ("sysctl: handle error writing UINT_MAX to u32 fields")
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 | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 81657b13bd53..30681afbdb70 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -583,9 +583,9 @@ static int do_proc_douintvec_conv(unsigned long *lvalp,
if (write) {
if (*lvalp > UINT_MAX)
return -EINVAL;
- *valp = *lvalp;
+ WRITE_ONCE(*valp, *lvalp);
} else {
- unsigned int val = *valp;
+ unsigned int val = READ_ONCE(*valp);
*lvalp = (unsigned long)val;
}
return 0;
--
2.35.1