releases/6.6.26/bpf-put-uprobe-link-s-path-and-task-in-release-callback.patch

   1 From e9c856cabefb71d47b2eeb197f72c9c88e9b45b0 Mon Sep 17 00:00:00 2001
   2 From: Andrii Nakryiko <andrii@kernel.org>
   3 Date: Wed, 27 Mar 2024 22:24:25 -0700
   4 Subject: bpf: put uprobe link's path and task in release callback
   5
   6 From: Andrii Nakryiko <andrii@kernel.org>
   7
   8 commit e9c856cabefb71d47b2eeb197f72c9c88e9b45b0 upstream.
   9
  10 There is no need to delay putting either path or task to deallocation
  11 step. It can be done right after bpf_uprobe_unregister. Between release
  12 and dealloc, there could be still some running BPF programs, but they
  13 don't access either task or path, only data in link->uprobes, so it is
  14 safe to do.
  15
  16 On the other hand, doing path_put() in dealloc callback makes this
  17 dealloc sleepable because path_put() itself might sleep. Which is
  18 problematic due to the need to call uprobe's dealloc through call_rcu(),
  19 which is what is done in the next bug fix patch. So solve the problem by
  20 releasing these resources early.
  21
  22 Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
  23 Link: https://lore.kernel.org/r/20240328052426.3042617-1-andrii@kernel.org
  24 Signed-off-by: Alexei Starovoitov <ast@kernel.org>
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26 ---
  27  kernel/trace/bpf_trace.c |    6 +++---
  28  1 file changed, 3 insertions(+), 3 deletions(-)
  29
  30 --- a/kernel/trace/bpf_trace.c
  31 +++ b/kernel/trace/bpf_trace.c
  32 @@ -3065,6 +3065,9 @@ static void bpf_uprobe_multi_link_releas
  33
  34         umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
  35         bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt);
  36 +       if (umulti_link->task)
  37 +               put_task_struct(umulti_link->task);
  38 +       path_put(&umulti_link->path);
  39  }
  40
  41  static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
  42 @@ -3072,9 +3075,6 @@ static void bpf_uprobe_multi_link_deallo
  43         struct bpf_uprobe_multi_link *umulti_link;
  44
  45         umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
  46 -       if (umulti_link->task)
  47 -               put_task_struct(umulti_link->task);
  48 -       path_put(&umulti_link->path);
  49         kvfree(umulti_link->uprobes);
  50         kfree(umulti_link);
  51  }