Then multiple threads are attaching/detaching fentry/fexit programs to
the same trampoline, we may call register_fentry on the same trampoline
twice: register_fentry(), unregister_fentry(), then register_fentry again.
This causes ftrace_set_filter_ip() for the same ip on tr->fops twice,
which leaves duplicated ip in tr->fops. The extra ip is not cleaned up
properly on unregister and thus causes failures with further register in
register_ftrace_direct_multi():
register_ftrace_direct_multi()
{
...
for (i = 0; i < size; i++) {
hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
if (ftrace_find_rec_direct(entry->ip))
goto out_unlock;
}
}
...
}
This can be triggered with parallel fentry/fexit tests with test_progs:
./test_progs -t fentry,fexit -j
Fix this by resetting tr->fops in ftrace_set_filter_ip(), so that there
will never be duplicated entries in tr->fops.
Fixes: 00963a2e75a8 ("bpf: Support bpf_trampoline on functions with IPMODIFY (e.g. livepatch)")
Reported-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Song Liu <[email protected]>
---
kernel/bpf/trampoline.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 42e387a12694..7ec7e23559ad 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -255,7 +255,7 @@ static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
return -ENOENT;
if (tr->func.ftrace_managed) {
- ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 0);
+ ftrace_set_filter_ip(tr->fops, (unsigned long)ip, 0, 1);
ret = register_ftrace_direct_multi(tr->fops, (long)new_addr);
} else {
ret = bpf_arch_text_poke(ip, BPF_MOD_CALL, NULL, new_addr);
--
2.30.2
On Fri, 29 Jul 2022 12:41:06 -0700
Song Liu <[email protected]> wrote:
> Then multiple threads are attaching/detaching fentry/fexit programs to
"When multiple threads"?
-- Steve
> the same trampoline, we may call register_fentry on the same trampoline
> twice: register_fentry(), unregister_fentry(), then register_fentry again.
> This causes ftrace_set_filter_ip() for the same ip on tr->fops twice,
> which leaves duplicated ip in tr->fops. The extra ip is not cleaned up
> properly on unregister and thus causes failures with further register in
> register_ftrace_direct_multi():
>
> register_ftrace_direct_multi()
> {
> ...
> for (i = 0; i < size; i++) {
> hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> if (ftrace_find_rec_direct(entry->ip))
> goto out_unlock;
> }
> }
> ...
> }
>
> This can be triggered with parallel fentry/fexit tests with test_progs:
>
> ./test_progs -t fentry,fexit -j
>
> Fix this by resetting tr->fops in ftrace_set_filter_ip(), so that there
> will never be duplicated entries in tr->fops.
>
Hello:
This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <[email protected]>:
On Fri, 29 Jul 2022 12:41:06 -0700 you wrote:
> Then multiple threads are attaching/detaching fentry/fexit programs to
> the same trampoline, we may call register_fentry on the same trampoline
> twice: register_fentry(), unregister_fentry(), then register_fentry again.
> This causes ftrace_set_filter_ip() for the same ip on tr->fops twice,
> which leaves duplicated ip in tr->fops. The extra ip is not cleaned up
> properly on unregister and thus causes failures with further register in
> register_ftrace_direct_multi():
>
> [...]
Here is the summary with links:
- [bpf-next] bpf: fix test_progs -j error with fentry/fexit tests
https://git.kernel.org/bpf/bpf-next/c/dc81f8d1e8ea
You are awesome, thank you!
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