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sysctl: Fix data races in proc_dointvec_jiffies().

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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_jiffies() to use READ_ONCE() and
WRITE_ONCE() internally to fix data-races on the sysctl side.  For now,
proc_dointvec_jiffies() 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>
This commit is contained in:
Kuniyuki Iwashima 2022-07-06 16:39:57 -07:00 committed by David S. Miller
parent c31bcc8fb8
commit e877820877
1 changed files with 5 additions and 2 deletions
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7
kernel/sysctl.c
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@ -1173,9 +1173,12 @@ static int do_proc_dointvec_jiffies_conv(bool *negp, unsigned long *lvalp,
if (write) {
if (*lvalp > INT_MAX / HZ)
return 1;
*valp = *negp ? -(*lvalp*HZ) : (*lvalp*HZ);
if (*negp)
WRITE_ONCE(*valp, -*lvalp * HZ);
else
WRITE_ONCE(*valp, *lvalp * HZ);
} else {
int val = *valp;
int val = READ_ONCE(*valp);
unsigned long lval;
if (val < 0) {
*negp = true;