From: Walter Wu <walter-zh.wu@mediatek.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
"Andrey Konovalov" <andreyknvl@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>, Oleg Nesterov <oleg@redhat.com>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
wsd_upstream <wsd_upstream@mediatek.com>,
<linux-mediatek@lists.infradead.org>
Subject: Re: [PATCH] task_work: kasan: record task_work_add() call stack
Date: Mon, 15 Mar 2021 17:38:22 +0800 [thread overview]
Message-ID: <1615801102.24887.4.camel@mtksdccf07> (raw)
In-Reply-To: <CACT4Y+YrFeRQkw+M8rpOF5169LFn9+puL3Dh1Kk1AOoKV-nyrQ@mail.gmail.com>
On Mon, 2021-03-15 at 07:58 +0100, 'Dmitry Vyukov' via kasan-dev wrote:
> On Mon, Mar 15, 2021 at 3:00 AM Walter Wu <walter-zh.wu@mediatek.com> wrote:
> >
> > Why record task_work_add() call stack?
> > Syzbot reports many use-after-free issues for task_work, see [1].
> > After see the free stack and the current auxiliary stack, we think
> > they are useless, we don't know where register the work, this work
> > may be the free call stack, so that we miss the root cause and
> > don't solve the use-after-free.
> >
> > Add task_work_add() call stack into KASAN auxiliary stack in
> > order to improve KASAN report. It is useful for programmers
> > to solve use-after-free issues.
> >
> > [1]: https://groups.google.com/g/syzkaller-bugs/search?q=kasan%20use-after-free%20task_work_run
> >
> > Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
> > Suggested-by: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Andrey Konovalov <andreyknvl@google.com>
> > Cc: Alexander Potapenko <glider@google.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Matthias Brugger <matthias.bgg@gmail.com>
> > Cc: Jens Axboe <axboe@kernel.dk>
> > Cc: Oleg Nesterov <oleg@redhat.com>
> > ---
> > kernel/task_work.c | 3 +++
> > mm/kasan/kasan.h | 2 +-
> > 2 files changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/task_work.c b/kernel/task_work.c
> > index 9cde961875c0..f255294377da 100644
> > --- a/kernel/task_work.c
> > +++ b/kernel/task_work.c
> > @@ -55,6 +55,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
> > break;
> > }
> >
> > + /* record the work call stack in order to print it in KASAN reports */
> > + kasan_record_aux_stack(work);
>
> I think this call should be done _before_ we actually queue the work,
> because this function may operate on non-current task.
> Consider, we queue the work, the other task already executes it and
> triggers use-after-free, now only now we record the stack.
agree, what do you think below change?
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -34,6 +34,9 @@ int task_work_add(struct task_struct *task, struct
callback_head *work,
{
struct callback_head *head;
+ /* record the work call stack in order to print it in KASAN reports
*/
+ kasan_record_aux_stack(work);
+
do {
head = READ_ONCE(task->task_works);
if (unlikely(head == &work_exited))
@@ -55,9 +58,6 @@ int task_work_add(struct task_struct *task, struct
callback_head *work,
break;
}
- /* record the work call stack in order to print it in KASAN reports
*/
- kasan_record_aux_stack(work);
-
return 0;
}
> Moreover, I think we can trigger use-after-free here ourselves while
> recording the aux stack. We queued the work, and the work can cause
> own free, so it's not necessary live by now.
Sorry, I don't fully know your meaning, do you mean we should add an
abort when detect use-after-free?
>
> > return 0;
> > }
> >
> > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> > index 3436c6bf7c0c..d300fe9415bd 100644
> > --- a/mm/kasan/kasan.h
> > +++ b/mm/kasan/kasan.h
> > @@ -146,7 +146,7 @@ struct kasan_alloc_meta {
> > struct kasan_track alloc_track;
> > #ifdef CONFIG_KASAN_GENERIC
> > /*
> > - * call_rcu() call stack is stored into struct kasan_alloc_meta.
> > + * Auxiliary stack is stored into struct kasan_alloc_meta.
> > * The free stack is stored into struct kasan_free_meta.
> > */
> > depot_stack_handle_t aux_stack[2];
> > --
> > 2.18.0
>
next prev parent reply other threads:[~2021-03-15 9:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-15 1:59 [PATCH] task_work: kasan: record task_work_add() call stack Walter Wu
2021-03-15 6:58 ` Dmitry Vyukov
2021-03-15 9:38 ` Walter Wu [this message]
2021-03-15 10:03 ` Dmitry Vyukov
2021-03-15 10:13 ` Walter Wu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1615801102.24887.4.camel@mtksdccf07 \
--to=walter-zh.wu@mediatek.com \
--cc=akpm@linux-foundation.org \
--cc=andreyknvl@google.com \
--cc=axboe@kernel.dk \
--cc=dvyukov@google.com \
--cc=glider@google.com \
--cc=kasan-dev@googlegroups.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=linux-mm@kvack.org \
--cc=matthias.bgg@gmail.com \
--cc=oleg@redhat.com \
--cc=ryabinin.a.a@gmail.com \
--cc=wsd_upstream@mediatek.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).