lkml.org 
[lkml]   [2022]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH bpf-next] bpf: fix test_progs -j error with fentry/fexit tests
Date
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 <andrii@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
---
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
\
 
 \ /
  Last update: 2022-07-29 21:42    [W:0.108 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site