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Date: Thu, 06 Jun 2024 06:27:38 -0700
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Subject: Re: [syzbot] possible deadlock in trie_delete_elem
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Subject: possible deadlock in trie_delete_elem
Author: norbert.kaminski@infogain.com

#syz test https://linux.googlesource.com/linux/kernel/git/torvalds/linux e3=
77d803b65ee4130213b3c041fc25fdfec1bd90

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 2d29bc0f21cc..75fdb8e3abaa 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2393,12 +2393,21 @@ void __bpf_trace_run(struct bpf_raw_tp_link *link, =
u64 *args)
        cant_sleep();

        // return if instrumentation disabled, see: bpf_disable_instrumenta=
tion
-       if (unlikely(__this_cpu_read(bpf_prog_active))) {
+       int instrumentation =3D unlikely(__this_cpu_read(bpf_prog_active));
+       if (instrumentation) {
+               printk("SKIP FOR INSTRUMENTATION: %s > %s > %p /%i =3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\n",
+                               prog->aux->name,
+                               link->btp->tp->name, prog, instrumentation)=
;
                bpf_prog_inc_misses_counter(prog);
                return;
        }

-       if (unlikely(this_cpu_inc_return(*(prog->active)) !=3D 1)) {
+       int active =3D this_cpu_inc_return(*(prog->active));
+       // printk("%s > %s > %p /%i\n", prog->aux->name, link->btp->tp->nam=
e, prog, active);
+       if (active !=3D 1) {
+               printk("SKIP FOR ACTIVE: %s > %s > %p /%i =3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\n",
+                               prog->aux->name,
+                               link->btp->tp->name, prog, active);
                bpf_prog_inc_misses_counter(prog);
                goto out;
        }
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 8d1507dd0724..e756262d8df7 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -168,12 +169,21 @@ static inline void release_probes(struct tracepoint_f=
unc *old)
 static void debug_print_probes(struct tracepoint_func *funcs)
 {
        int i;
+       struct bpf_raw_tp_link *link;

        if (!tracepoint_debug || !funcs)
                return;

-       for (i =3D 0; funcs[i].func; i++)
-               printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
+       for (i =3D 0; funcs[i].func; i++) {
+               link =3D funcs[i].data;
+               int active =3D this_cpu_read(*(link->link.prog->active));
+               printk("Probe %d : %p / %p: %s/%d / %i\n", i,
+                               funcs[i].func,
+                               link,
+                               link->link.prog->aux->name,
+                               active,
+                               funcs[i].prio);
+       }
 }

 static struct tracepoint_func *
@@ -298,6 +308,8 @@ static enum tp_func_state nr_func_state(const struct tr=
acepoint_func *tp_funcs)
 {
        if (!tp_funcs)
                return TP_FUNC_0;
+       if (!tp_funcs[0].func)
+               return TP_FUNC_0;
        if (!tp_funcs[1].func)
                return TP_FUNC_1;
        if (!tp_funcs[2].func)
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