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sysctl: Fix data races in proc_dointvec().

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[ Upstream commit 1f1be04b4d ]

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: 1da177e4c3 ("Linux-2.6.12-rc2")
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>
This commit is contained in:
Kuniyuki Iwashima 2022-07-06 16:39:52 -07:00 • committed by Greg Kroah-Hartman
commit 80cc28a4b4
1 changed files with 3 additions and 3 deletions
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6
kernel/sysctl.c
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@ -557,14 +557,14 @@ 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;