@@ -2391,7 +2391,9 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args)
struct bpf_trace_run_ctx run_ctx;
cant_sleep();
- if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
+
+ // if the instrumentation is not disabled disable recurrence and go
+ if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
bpf_prog_inc_misses_counter(prog);
goto out;
}
@@ -2405,7 +2407,7 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, u64 *args)
bpf_reset_run_ctx(old_run_ctx);
out:
- this_cpu_dec(*(prog->active));
+ __this_cpu_dec(bpf_prog_active);
}
#define UNPACK(...) __VA_ARGS__
On bpf syscall map operations the bpf_disable_instrumentation function is called for the reason described in the comment to the function. The description matches the bug case. The function increments a per CPU integer variable bpf_prog_active. The variable is not processed in the bpf trace path. The fix implements a similar processing as for kprobe handling. The fix degrades the bpf tracing by skipping some eBPF trace sequences that otherwise might yield deadlock. Reported-by: syzbot+9d95beb2a3c260622518@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9d95beb2a3c260622518 Link: https://lore.kernel.org/all/000000000000adb08b061413919e@google.com/T/ Signed-off-by: Wojciech Gładysz <wojciech.gladysz@infogain.com> --- kernel/trace/bpf_trace.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)