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    Subject[PATCH 5.15 053/167] sysctl: Fix data races in proc_dointvec_minmax().
    Date
    From: Kuniyuki Iwashima <kuniyu@amazon.com>

    [ Upstream commit f613d86d014b6375a4085901de39406598121e35 ]

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

    Fixes: 1da177e4c3f4 ("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>
    ---
    kernel/sysctl.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/kernel/sysctl.c b/kernel/sysctl.c
    index b152e0a30a2b..f5134435fb9c 100644
    --- a/kernel/sysctl.c
    +++ b/kernel/sysctl.c
    @@ -988,7 +988,7 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
    if ((param->min && *param->min > tmp) ||
    (param->max && *param->max < tmp))
    return -EINVAL;
    - *valp = tmp;
    + WRITE_ONCE(*valp, tmp);
    }

    return 0;
    --
    2.35.1


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