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    Subject[PATCH 5.15 536/917] bpf: Fixes possible race in update_prog_stats() for 32bit arches
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit d979617aa84d96acca44c2f5778892b4565e322f ]

    It seems update_prog_stats() suffers from same issue fixed
    in the prior patch:

    As it can run while interrupts are enabled, it could
    be re-entered and the u64_stats syncp could be mangled.

    Fixes: fec56f5890d9 ("bpf: Introduce BPF trampoline")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Link: https://lore.kernel.org/bpf/20211026214133.3114279-3-eric.dumazet@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/bpf/trampoline.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
    index fe1e857324e66..d3a307a8c42b9 100644
    --- a/kernel/bpf/trampoline.c
    +++ b/kernel/bpf/trampoline.c
    @@ -585,11 +585,13 @@ static void notrace update_prog_stats(struct bpf_prog *prog,
    * Hence check that 'start' is valid.
    */
    start > NO_START_TIME) {
    + unsigned long flags;
    +
    stats = this_cpu_ptr(prog->stats);
    - u64_stats_update_begin(&stats->syncp);
    + flags = u64_stats_update_begin_irqsave(&stats->syncp);
    stats->cnt++;
    stats->nsecs += sched_clock() - start;
    - u64_stats_update_end(&stats->syncp);
    + u64_stats_update_end_irqrestore(&stats->syncp, flags);
    }
    }

    --
    2.33.0


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