sysctl: Fix data-races in proc_dou8vec_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_dou8vec_minmax() to use READ_ONCE() and
WRITE_ONCE() internally to fix data-races on the sysctl side.  For now,
proc_dou8vec_minmax() itself is tolerant to a data-race, but we still
need to add annotations on the other subsystem's side.

Fixes: fe2a51c7fe7d ("sysctl: add proc_dou8vec_minmax()")
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 bf9383d17e1bb6f81bafcb9061ff3156045b7683..b016d68da08a0dce2a4f010e412299a8125d6722 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1007,13 +1007,13 @@ int proc_dou8vec_minmax(struct ctl_table *table, int write,
 
        tmp.maxlen = sizeof(val);
        tmp.data = &val;
-       val = *data;
+       val = READ_ONCE(*data);
        res = do_proc_douintvec(&tmp, write, buffer, lenp, ppos,
                                do_proc_douintvec_minmax_conv, &param);
        if (res)
                return res;
        if (write)
-               *data = val;
+               WRITE_ONCE(*data, val);
        return 0;
 }
 EXPORT_SYMBOL_GPL(proc_dou8vec_minmax);