This is a note to let you know that I've just added the patch titled
bpf: put uprobe link's path and task in release callback
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-put-uprobe-link-s-path-and-task-in-release-callback.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e9c856cabefb71d47b2eeb197f72c9c88e9b45b0 Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andrii@xxxxxxxxxx>
Date: Wed, 27 Mar 2024 22:24:25 -0700
Subject: bpf: put uprobe link's path and task in release callback
From: Andrii Nakryiko <andrii@xxxxxxxxxx>
commit e9c856cabefb71d47b2eeb197f72c9c88e9b45b0 upstream.
There is no need to delay putting either path or task to deallocation
step. It can be done right after bpf_uprobe_unregister. Between release
and dealloc, there could be still some running BPF programs, but they
don't access either task or path, only data in link->uprobes, so it is
safe to do.
On the other hand, doing path_put() in dealloc callback makes this
dealloc sleepable because path_put() itself might sleep. Which is
problematic due to the need to call uprobe's dealloc through call_rcu(),
which is what is done in the next bug fix patch. So solve the problem by
releasing these resources early.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240328052426.3042617-1-andrii@xxxxxxxxxx
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/bpf_trace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3142,6 +3142,9 @@ static void bpf_uprobe_multi_link_releas
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt);
+ if (umulti_link->task)
+ put_task_struct(umulti_link->task);
+ path_put(&umulti_link->path);
}
static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
@@ -3149,9 +3152,6 @@ static void bpf_uprobe_multi_link_deallo
struct bpf_uprobe_multi_link *umulti_link;
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
- if (umulti_link->task)
- put_task_struct(umulti_link->task);
- path_put(&umulti_link->path);
kvfree(umulti_link->uprobes);
kfree(umulti_link);
}
Patches currently in stable-queue which might be from andrii@xxxxxxxxxx are
queue-6.8/bpf-support-deferring-bpf_link-dealloc-to-after-rcu-grace-period.patch
queue-6.8/bpf-put-uprobe-link-s-path-and-task-in-release-callback.patch
queue-6.8/bpf-protect-against-int-overflow-for-stack-access-si.patch
