Commit 1f1be04b authored Jul 06, 2022 by Kuniyuki Iwashima Committed by David S. Miller Jul 08, 2022

sysctl: Fix data races in proc_dointvec().



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: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 820b8963

kernel/sysctl.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -446,14 +446,14 @@ 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;