* [PATCH bpf-next v3] bpf: log error code on trampoline unlink failure
@ 2026-07-28 6:26 xu.xin16
2026-07-28 8:08 ` Leon Hwang
0 siblings, 1 reply; 2+ messages in thread
From: xu.xin16 @ 2026-07-28 6:26 UTC (permalink / raw)
To: ast, daniel, john.fastabend, andrii, eddyz87, memxor, martin.lau,
song, yonghong.song, jolsa, emil, linux-kernel, leon.hwang
Cc: bpf
From: xu xin <xu.xin16@zte.com.cn>
Replace silent WARN_ON_ONCE with WARN_ONCE that prints the actual error
code from bpf_trampoline_unlink_prog(). This aids debugging of race
conditions during link teardown, while keeping the warning rate limited
to avoid log flooding.
This will be very helpful for speeding up trouble-shooting of some crash
UAF due to bpf_trampoline_unlink_prog failures.
No change to unlink behavior.
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
Change log
V2->v3:
Add up the case in bpf_trampoline_multi_detach. And remove the unneeded 'if (err)'
v1->v2:
1) clean the subject name by remove 'syscall' suggested by Leon Hwang
https://lore.kernel.org/all/20a444b2-aeed-4af8-ba76-e994e2c14087@linux.dev/
2) Add up the missed case in kernel/bpf/trampoline.c:bpf_shim_tramp_link_release()
kernel/bpf/syscall.c | 8 +++++---
kernel/bpf/trampoline.c | 12 ++++++++----
2 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6db306d23b47..52c57f8beb37 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3626,10 +3626,12 @@ static void bpf_tracing_link_release(struct bpf_link *link)
{
struct bpf_tracing_link *tr_link =
container_of(link, struct bpf_tracing_link, link.link);
+ int err;
- WARN_ON_ONCE(bpf_trampoline_unlink_prog(&tr_link->link.node,
- tr_link->trampoline,
- tr_link->tgt_prog));
+ err = bpf_trampoline_unlink_prog(&tr_link->link.node,
+ tr_link->trampoline,
+ tr_link->tgt_prog);
+ WARN_ONCE(err, "bpf_trampoline_unlink_prog returns error: %d\n", err);
bpf_trampoline_put(tr_link->trampoline);
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 1a721fc4bef5..a34ddb97ff6b 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -997,12 +997,15 @@ static void bpf_shim_tramp_link_release(struct bpf_link *link)
{
struct bpf_shim_tramp_link *shim_link =
container_of(link, struct bpf_shim_tramp_link, link.link);
+ int err;
/* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
if (!shim_link->trampoline)
return;
- WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link.node, shim_link->trampoline, NULL));
+ err = bpf_trampoline_unlink_prog(&shim_link->link.node, shim_link->trampoline, NULL);
+ WARN_ONCE(err, "bpf_trampoline_unlink_prog returns error: %d\n", err);
+
bpf_trampoline_put(shim_link->trampoline);
}
@@ -1712,15 +1715,16 @@ int bpf_trampoline_multi_detach(struct bpf_prog *prog, struct bpf_tracing_multi_
{
struct bpf_tracing_multi_data *data = &link->data;
struct bpf_tracing_multi_node *mnode;
- int i;
+ int i, err;
trampoline_lock_all();
for_each_mnode(mnode, link) {
data->entry = &mnode->entry;
bpf_trampoline_multi_attach_init(mnode->trampoline);
- WARN_ON_ONCE(__bpf_trampoline_unlink_prog(&mnode->node, mnode->trampoline,
- NULL, &trampoline_multi_ops, data));
+ err = __bpf_trampoline_unlink_prog(&mnode->node, mnode->trampoline,NULL,
+ &trampoline_multi_ops, data);
+ WARN_ONCE(err, "__bpf_trampoline_unlink_prog returns error: %d\n", err);
}
if (ftrace_hash_count(data->unreg))
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH bpf-next v3] bpf: log error code on trampoline unlink failure
2026-07-28 6:26 [PATCH bpf-next v3] bpf: log error code on trampoline unlink failure xu.xin16
@ 2026-07-28 8:08 ` Leon Hwang
0 siblings, 0 replies; 2+ messages in thread
From: Leon Hwang @ 2026-07-28 8:08 UTC (permalink / raw)
To: xu.xin16, ast, daniel, john.fastabend, andrii, eddyz87, memxor,
martin.lau, song, yonghong.song, jolsa, emil, linux-kernel
Cc: bpf
On 28/7/26 14:26, xu.xin16@zte.com.cn wrote:
> From: xu xin <xu.xin16@zte.com.cn>
>
> Replace silent WARN_ON_ONCE with WARN_ONCE that prints the actual error
> code from bpf_trampoline_unlink_prog(). This aids debugging of race
> conditions during link teardown, while keeping the warning rate limited
> to avoid log flooding.
>
> This will be very helpful for speeding up trouble-shooting of some crash
> UAF due to bpf_trampoline_unlink_prog failures.
>
> No change to unlink behavior.
>
> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Better to use Xu Xin as your formal name.
> ---
> Change log
> V2->v3:
> Add up the case in bpf_trampoline_multi_detach. And remove the unneeded 'if (err)'
>
> v1->v2:
> 1) clean the subject name by remove 'syscall' suggested by Leon Hwang
> https://lore.kernel.org/all/20a444b2-aeed-4af8-ba76-e994e2c14087@linux.dev/
> 2) Add up the missed case in kernel/bpf/trampoline.c:bpf_shim_tramp_link_release()
>
> kernel/bpf/syscall.c | 8 +++++---
> kernel/bpf/trampoline.c | 12 ++++++++----
> 2 files changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 6db306d23b47..52c57f8beb37 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3626,10 +3626,12 @@ static void bpf_tracing_link_release(struct bpf_link *link)
> {
> struct bpf_tracing_link *tr_link =
> container_of(link, struct bpf_tracing_link, link.link);
> + int err;
>
> - WARN_ON_ONCE(bpf_trampoline_unlink_prog(&tr_link->link.node,
> - tr_link->trampoline,
> - tr_link->tgt_prog));
> + err = bpf_trampoline_unlink_prog(&tr_link->link.node,
> + tr_link->trampoline,
> + tr_link->tgt_prog);
> + WARN_ONCE(err, "bpf_trampoline_unlink_prog returns error: %d\n", err);
>
> bpf_trampoline_put(tr_link->trampoline);
>
> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index 1a721fc4bef5..a34ddb97ff6b 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -997,12 +997,15 @@ static void bpf_shim_tramp_link_release(struct bpf_link *link)
> {
> struct bpf_shim_tramp_link *shim_link =
> container_of(link, struct bpf_shim_tramp_link, link.link);
> + int err;
>
> /* paired with 'shim_link->trampoline = tr' in bpf_trampoline_link_cgroup_shim */
> if (!shim_link->trampoline)
> return;
>
> - WARN_ON_ONCE(bpf_trampoline_unlink_prog(&shim_link->link.node, shim_link->trampoline, NULL));
> + err = bpf_trampoline_unlink_prog(&shim_link->link.node, shim_link->trampoline, NULL);
> + WARN_ONCE(err, "bpf_trampoline_unlink_prog returns error: %d\n", err);
> +
> bpf_trampoline_put(shim_link->trampoline);
> }
>
> @@ -1712,15 +1715,16 @@ int bpf_trampoline_multi_detach(struct bpf_prog *prog, struct bpf_tracing_multi_
> {
> struct bpf_tracing_multi_data *data = &link->data;
> struct bpf_tracing_multi_node *mnode;
> - int i;
> + int i, err;
>
> trampoline_lock_all();
>
> for_each_mnode(mnode, link) {
> data->entry = &mnode->entry;
> bpf_trampoline_multi_attach_init(mnode->trampoline);
> - WARN_ON_ONCE(__bpf_trampoline_unlink_prog(&mnode->node, mnode->trampoline,
> - NULL, &trampoline_multi_ops, data));
> + err = __bpf_trampoline_unlink_prog(&mnode->node, mnode->trampoline,NULL,
NIT: a space is missing at the position between ',' and 'NULL'.
> + &trampoline_multi_ops, data);
NIT: align '&' with previous line's '&'.
Other than that,
Acked-by: Leon Hwang <leon.hwang@linux.dev>
> + WARN_ONCE(err, "__bpf_trampoline_unlink_prog returns error: %d\n", err);
> }
>
> if (ftrace_hash_count(data->unreg))
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2026-07-28 6:26 [PATCH bpf-next v3] bpf: log error code on trampoline unlink failure xu.xin16
2026-07-28 8:08 ` Leon Hwang
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