bpf: Fixes possible race in update_prog_stats() for 32bit arches

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

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 39eaaff81953da6006702635fd67d08dd4a7daa2..e5963de368ed34874414d097bc6614ff7e168dd3 100644 (file)
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -586,11 +586,13 @@ 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);
        }
 }