Commit 0e3135d3 authored by He Fengqing's avatar He Fengqing Committed by Alexei Starovoitov
Browse files

bpf: Fix possible race in inc_misses_counter 



It seems inc_misses_counter() suffers from same issue fixed in
the commit d979617a ("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: 9ed9e9ba ("bpf: Count the number of times recursion was prevented")
Signed-off-by: default avatarHe Fengqing <hefengqing@huawei.com>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20220122102936.1219518-1-hefengqing@huawei.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 63ee956f

kernel/bpf/trampoline.c

+3 −2
Original line number Diff line number Diff line
@@ -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