bpf: Unbreak BPF_PROG_TYPE_KPROBE when kprobe is called via do_int3

The commit 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()")
converted do_int3 handler to be "NMI-like".
That made old if (in_nmi()) check abort execution of bpf programs
attached to kprobe when kprobe is firing via int3
(For example when kprobe is placed in the middle of the function).
Remove the check to restore user visible behavior.

Fixes: 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()")
Reported-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/bpf/20210203070636.70926-1-alexei.starovoitov@gmail.com

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 6c0018a..7644002 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -96,9 +96,6 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 {
        unsigned int ret;
 
-       if (in_nmi()) /* not supported yet */
-               return 1;
-
        cant_sleep();
 
        if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {