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    Subject[PATCH 5.10 043/112] sysctl: Fix data races in proc_douintvec().
    Date
    From: Kuniyuki Iwashima <kuniyu@amazon.com>

    [ Upstream commit 4762b532ec9539755aab61445d5da6e1926ccb99 ]

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

    Fixes: e7d316a02f68 ("sysctl: handle error writing UINT_MAX to u32 fields")
    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 | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/kernel/sysctl.c b/kernel/sysctl.c
    index 81657b13bd53..30681afbdb70 100644
    --- a/kernel/sysctl.c
    +++ b/kernel/sysctl.c
    @@ -583,9 +583,9 @@ static int do_proc_douintvec_conv(unsigned long *lvalp,
    if (write) {
    if (*lvalp > UINT_MAX)
    return -EINVAL;
    - *valp = *lvalp;
    + WRITE_ONCE(*valp, *lvalp);
    } else {
    - unsigned int val = *valp;
    + unsigned int val = READ_ONCE(*valp);
    *lvalp = (unsigned long)val;
    }
    return 0;
    --
    2.35.1


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