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authorJiri Olsa <jolsa@kernel.org>2023-07-25 10:42:05 +0200
committerAlexei Starovoitov <ast@kernel.org>2023-07-25 17:05:53 -0700
commitf2c67a3e60d1071b65848efaa8c3b66c363dd025 (patch)
treef7644b4bb37f372e3836cd6b23a526370bf92b4b /kernel
parent284779dbf4e98753458708783af8c35630674a21 (diff)
bpf: Disable preemption in bpf_perf_event_output
The nesting protection in bpf_perf_event_output relies on disabled preemption, which is guaranteed for kprobes and tracepoints. However bpf_perf_event_output can be also called from uprobes context through bpf_prog_run_array_sleepable function which disables migration, but keeps preemption enabled. This can cause task to be preempted by another one inside the nesting protection and lead eventually to two tasks using same perf_sample_data buffer and cause crashes like: kernel tried to execute NX-protected page - exploit attempt? (uid: 0) BUG: unable to handle page fault for address: ffffffff82be3eea ... Call Trace: ? __die+0x1f/0x70 ? page_fault_oops+0x176/0x4d0 ? exc_page_fault+0x132/0x230 ? asm_exc_page_fault+0x22/0x30 ? perf_output_sample+0x12b/0x910 ? perf_event_output+0xd0/0x1d0 ? bpf_perf_event_output+0x162/0x1d0 ? bpf_prog_c6271286d9a4c938_krava1+0x76/0x87 ? __uprobe_perf_func+0x12b/0x540 ? uprobe_dispatcher+0x2c4/0x430 ? uprobe_notify_resume+0x2da/0xce0 ? atomic_notifier_call_chain+0x7b/0x110 ? exit_to_user_mode_prepare+0x13e/0x290 ? irqentry_exit_to_user_mode+0x5/0x30 ? asm_exc_int3+0x35/0x40 Fixing this by disabling preemption in bpf_perf_event_output. Cc: stable@vger.kernel.org Fixes: 8c7dcb84e3b7 ("bpf: implement sleepable uprobes by chaining gps") Acked-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20230725084206.580930-2-jolsa@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/bpf_trace.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 5f2dcabad202..bf18a53731b0 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -661,8 +661,7 @@ static DEFINE_PER_CPU(int, bpf_trace_nest_level);
BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
u64, flags, void *, data, u64, size)
{
- struct bpf_trace_sample_data *sds = this_cpu_ptr(&bpf_trace_sds);
- int nest_level = this_cpu_inc_return(bpf_trace_nest_level);
+ struct bpf_trace_sample_data *sds;
struct perf_raw_record raw = {
.frag = {
.size = size,
@@ -670,7 +669,11 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
},
};
struct perf_sample_data *sd;
- int err;
+ int nest_level, err;
+
+ preempt_disable();
+ sds = this_cpu_ptr(&bpf_trace_sds);
+ nest_level = this_cpu_inc_return(bpf_trace_nest_level);
if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(sds->sds))) {
err = -EBUSY;
@@ -688,9 +691,9 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
perf_sample_save_raw_data(sd, &raw);
err = __bpf_perf_event_output(regs, map, flags, sd);
-
out:
this_cpu_dec(bpf_trace_nest_level);
+ preempt_enable();
return err;
}