Commit 283ca526 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Alexei Starovoitov
Browse files

bpf: fix corruption on concurrent perf_event_output calls 



When tracing and networking programs are both attached in the
system and both use event-output helpers that eventually call
into perf_event_output(), then we could end up in a situation
where the tracing attached program runs in user context while
a cls_bpf program is triggered on that same CPU out of softirq
context.

Since both rely on the same per-cpu perf_sample_data, we could
potentially corrupt it. This can only ever happen in a combination
of the two types; all tracing programs use a bpf_prog_active
counter to bail out in case a program is already running on
that CPU out of a different context. XDP and cls_bpf programs
by themselves don't have this issue as they run in the same
context only. Therefore, split both perf_sample_data so they
cannot be accessed from each other.

Fixes: 20b9d7ac ("bpf: avoid excessive stack usage for perf_sample_data")
Reported-by: default avatarAlexei Starovoitov <ast@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Tested-by: default avatarSong Liu <songliubraving@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 30791ac4

kernel/trace/bpf_trace.c

+12 −7
Original line number Diff line number Diff line
@@ -343,14 +343,13 @@ static const struct bpf_func_proto bpf_perf_event_read_value_proto = { 
	.arg4_type	= ARG_CONST_SIZE,

};



static DEFINE_PER_CPU(struct perf_sample_data, bpf_sd);

static DEFINE_PER_CPU(struct perf_sample_data, bpf_trace_sd);



static __always_inline u64

__bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,

			u64 flags, struct perf_raw_record *raw)

			u64 flags, struct perf_sample_data *sd)

{

	struct bpf_array *array = container_of(map, struct bpf_array, map);

	struct perf_sample_data *sd = this_cpu_ptr(&bpf_sd);

	unsigned int cpu = smp_processor_id();

	u64 index = flags & BPF_F_INDEX_MASK;

	struct bpf_event_entry *ee;
@@ -373,8 +372,6 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map, 
	if (unlikely(event->oncpu != cpu))

		return -EOPNOTSUPP;



	perf_sample_data_init(sd, 0, 0);

	sd->raw = raw;

	perf_event_output(event, sd, regs);

	return 0;

}
@@ -382,6 +379,7 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map, 
BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,

	   u64, flags, void *, data, u64, size)

{

	struct perf_sample_data *sd = this_cpu_ptr(&bpf_trace_sd);

	struct perf_raw_record raw = {

		.frag = {

			.size = size,
@@ -392,7 +390,10 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map, 
	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))

		return -EINVAL;



	return __bpf_perf_event_output(regs, map, flags, &raw);

	perf_sample_data_init(sd, 0, 0);

	sd->raw = &raw;



	return __bpf_perf_event_output(regs, map, flags, sd);

}



static const struct bpf_func_proto bpf_perf_event_output_proto = {
@@ -407,10 +408,12 @@ static const struct bpf_func_proto bpf_perf_event_output_proto = { 
};



static DEFINE_PER_CPU(struct pt_regs, bpf_pt_regs);

static DEFINE_PER_CPU(struct perf_sample_data, bpf_misc_sd);



u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,

		     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)

{

	struct perf_sample_data *sd = this_cpu_ptr(&bpf_misc_sd);

	struct pt_regs *regs = this_cpu_ptr(&bpf_pt_regs);

	struct perf_raw_frag frag = {

		.copy		= ctx_copy,
@@ -428,8 +431,10 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size, 
	};



	perf_fetch_caller_regs(regs);

	perf_sample_data_init(sd, 0, 0);

	sd->raw = &raw;



	return __bpf_perf_event_output(regs, map, flags, &raw);

	return __bpf_perf_event_output(regs, map, flags, sd);

}



BPF_CALL_0(bpf_get_current_task)

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