sysctl: Fix data races in proc_douintvec().

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>

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c8a05655ae601c82e40aef7946091bb6ef8ffff4..2ab8c2a37e8f759e6bcce3ba3188ccd330714e5e 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -472,9 +472,9 @@ 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;