From: Steven Rostedt <rostedt@goodmis.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Matt Mullins <mmullins@mmlx.us>, Ingo Molnar <mingo@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Dmitry Vyukov <dvyukov@google.com>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>, netdev <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>, Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] tracepoint: Do not fail unregistering a probe due to memory allocation
Date: Mon, 16 Nov 2020 18:16:38 -0500 [thread overview]
Message-ID: <20201116181638.6b0de6f7@gandalf.local.home> (raw)
In-Reply-To: <20201116175107.02db396d@gandalf.local.home>
On Mon, 16 Nov 2020 17:51:07 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> [ Kees, I added you because you tend to know about these things.
> Is it OK to assign a void func(void) that doesn't do anything and returns
> nothing to a function pointer that could be call with parameters? We need
> to add stubs for tracepoints when we fail to allocate a new array on
> removal of a callback, but the callbacks do have arguments, but the stub
> called does not have arguments.
>
> Matt, Does this patch fix the error your patch was trying to fix?
> ]
>
> The list of tracepoint callbacks is managed by an array that is protected
> by RCU. To update this array, a new array is allocated, the updates are
> copied over to the new array, and then the list of functions for the
> tracepoint is switched over to the new array. After a completion of an RCU
> grace period, the old array is freed.
>
> This process happens for both adding a callback as well as removing one.
> But on removing a callback, if the new array fails to be allocated, the
> callback is not removed, and may be used after it is freed by the clients
> of the tracepoint.
>
> There's really no reason to fail if the allocation for a new array fails
> when removing a function. Instead, the function can simply be replaced by a
> stub function that could be cleaned up on the next modification of the
> array. That is, instead of calling the function registered to the
> tracepoint, it would call a stub function in its place.
>
> Link: https://lore.kernel.org/r/20201115055256.65625-1-mmullins@mmlx.us
>
> Cc: stable@vger.kernel.org
> Fixes: 97e1c18e8d17b ("tracing: Kernel Tracepoints")
> Reported-by: syzbot+83aa762ef23b6f0d1991@syzkaller.appspotmail.com
> Reported-by: syzbot+d29e58bb557324e55e5e@syzkaller.appspotmail.com
> Reported-by: Matt Mullins <mmullins@mmlx.us>
Forgot my:
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
and tested with adding this (just to see if paths are hit).
-- Steve
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 774b3733cbbe..96f081ff5284 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -167,6 +167,7 @@ func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
/* Need to copy one at a time to remove stubs */
int probes = 0;
+ printk("HERE stub_funcs=%d\n", stub_funcs);
pos = -1;
for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
if (old[nr_probes].func == tp_stub_func)
@@ -235,7 +236,7 @@ static void *func_remove(struct tracepoint_func **funcs,
int j = 0;
/* N -> M, (N > 1, M > 0) */
/* + 1 for NULL */
- new = allocate_probes(nr_probes - nr_del + 1, __GFP_NOFAIL);
+ new = NULL; //allocate_probes(nr_probes - nr_del + 1, __GFP_NOFAIL);
if (new) {
for (i = 0; old[i].func; i++)
if ((old[i].func != tp_func->func
next prev parent reply other threads:[~2020-11-16 23:17 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 22:51 [PATCH] tracepoint: Do not fail unregistering a probe due to memory allocation Steven Rostedt
2020-11-16 23:16 ` Steven Rostedt [this message]
2020-11-17 19:15 ` Mathieu Desnoyers
2020-11-17 19:21 ` Steven Rostedt
2020-11-17 19:47 ` Mathieu Desnoyers
2020-11-17 20:34 ` Steven Rostedt
2020-11-17 20:58 ` Steven Rostedt
2020-11-17 21:22 ` Mathieu Desnoyers
2020-11-17 22:16 ` Steven Rostedt
2020-11-17 23:08 ` Mathieu Desnoyers
2020-11-18 1:11 ` Steven Rostedt
2020-11-17 21:08 ` Mathieu Desnoyers
2020-11-18 13:21 ` violating function pointer signature Peter Zijlstra
2020-11-18 13:59 ` Florian Weimer
2020-11-18 14:12 ` Peter Zijlstra
2020-11-18 14:18 ` Florian Weimer
2020-11-18 14:34 ` [PATCH v3] tracepoint: Do not fail unregistering a probe due to memory allocation Steven Rostedt
2020-11-24 5:59 ` Matt Mullins
2020-11-18 14:22 ` violating function pointer signature Steven Rostedt
2020-11-18 19:46 ` Alexei Starovoitov
2020-11-18 20:02 ` Steven Rostedt
2020-11-18 14:02 ` Steven Rostedt
2020-11-18 16:01 ` Mathieu Desnoyers
2020-11-18 16:19 ` David Laight
2020-11-18 16:50 ` Nick Desaulniers
2020-11-18 17:17 ` Steven Rostedt
2020-11-18 18:12 ` Segher Boessenkool
2020-11-18 18:31 ` Florian Weimer
2020-11-18 18:55 ` Segher Boessenkool
2020-11-18 18:58 ` Steven Rostedt
2020-11-18 18:59 ` Steven Rostedt
2020-11-18 19:11 ` Segher Boessenkool
2020-11-18 19:33 ` Steven Rostedt
2020-11-18 19:48 ` Segher Boessenkool
2020-11-18 20:44 ` Steven Rostedt
2020-11-19 8:21 ` Peter Zijlstra
2020-11-19 8:36 ` Peter Zijlstra
2020-11-19 14:37 ` Segher Boessenkool
2020-11-19 14:59 ` Steven Rostedt
2020-11-19 16:35 ` Segher Boessenkool
2020-11-19 17:42 ` David Laight
2020-11-19 19:27 ` Segher Boessenkool
2020-11-19 17:04 ` Alexei Starovoitov
2020-11-19 17:30 ` Steven Rostedt
2020-11-20 1:31 ` Nick Desaulniers
2020-11-17 21:33 ` [PATCH] tracepoint: Do not fail unregistering a probe due to memory allocation Kees Cook
2020-11-17 22:19 ` Steven Rostedt
2020-11-17 23:12 ` Mathieu Desnoyers
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=20201116181638.6b0de6f7@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=andriin@fb.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=dvyukov@google.com \
--cc=john.fastabend@gmail.com \
--cc=kafai@fb.com \
--cc=keescook@chromium.org \
--cc=kpsingh@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@redhat.com \
--cc=mmullins@mmlx.us \
--cc=netdev@vger.kernel.org \
--cc=songliubraving@fb.com \
--cc=yhs@fb.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).