bpf: Fix possible race in inc_misses_counter

It seems inc_misses_counter() suffers from same issue fixed in
the commit d979617aa84d ("bpf: Fixes possible race in update_prog_stats()
for 32bit arches"):
As it can run while interrupts are enabled, it could
be re-entered and the u64_stats syncp could be mangled.

Fixes: 9ed9e9ba2337 ("bpf: Count the number of times recursion was prevented")
Signed-off-by: He Fengqing <hefengqing@huawei.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20220122102936.1219518-1-hefengqing@huawei.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4b6974a195c138a3a69611408473c1c6d0d8f99f..5e7edf913060129bad0271924bb40f7777a137d2 100644 (file)
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -550,11 +550,12 @@ static __always_inline u64 notrace bpf_prog_start_time(void)
 static void notrace inc_misses_counter(struct bpf_prog *prog)
 {
        struct bpf_prog_stats *stats;
+       unsigned int flags;
 
        stats = this_cpu_ptr(prog->stats);
-       u64_stats_update_begin(&stats->syncp);
+       flags = u64_stats_update_begin_irqsave(&stats->syncp);
        u64_stats_inc(&stats->misses);
-       u64_stats_update_end(&stats->syncp);
+       u64_stats_update_end_irqrestore(&stats->syncp, flags);
 }
 
 /* The logic is similar to bpf_prog_run(), but with an explicit