sysctl: Fix data races in proc_douintvec_minmax().

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>

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4d87832367f2046143aa579c0f6082323a44edf8..379721a03d412a7190e5439a69a65528a869a9ce 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -923,7 +923,7 @@ 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;