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sysctl: Fix data races in proc_doulongvec_minmax().

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[ Upstream commit c31bcc8fb8 ]

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_doulongvec_minmax() to use READ_ONCE() and
WRITE_ONCE() internally to fix data-races on the sysctl side.  For now,
proc_doulongvec_minmax() 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 16:39:56 -07:00 • committed by Greg Kroah-Hartman
commit a5ee448d38
1 changed files with 2 additions and 2 deletions
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4
kernel/sysctl.c
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@ -1193,9 +1193,9 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table,
err = -EINVAL; err = -EINVAL;
break; break;
} }
*i = val; WRITE_ONCE(*i, val);
} else { } else {
val = convdiv * (*i) / convmul; val = convdiv * READ_ONCE(*i) / convmul;
if (!first) if (!first)
proc_put_char(&buffer, &left, '\t'); proc_put_char(&buffer, &left, '\t');
proc_put_long(&buffer, &left, val, false); proc_put_long(&buffer, &left, val, false);