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Message-Id: <20221114104837.9b284586fcce589e0e7e6a42@kernel.org>
Date: Mon, 14 Nov 2022 10:48:37 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Li Huafei <lihuafei1@...wei.com>
Cc: <naveen.n.rao@...ux.ibm.com>, <anil.s.keshavamurthy@...el.com>,
<davem@...emloft.net>, <rostedt@...dmis.org>,
<joe.lawrence@...hat.com>, <zhaogongyi@...wei.com>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kprobes: Skip clearing aggrprobe's post_handler in
kprobe-on-ftrace case
On Sat, 12 Nov 2022 15:00:00 +0800
Li Huafei <lihuafei1@...wei.com> wrote:
> In __unregister_kprobe_top(), if the currently unregistered probe has
> post_handler but other child probes of the aggrprobe do not have
> post_handler, the post_handler of the aggrprobe is cleared. If this is
> a ftrace-based probe, there is a problem. In later calls to
> disarm_kprobe(), we will use kprobe_ftrace_ops because post_handler is
> NULL. But we're armed with kprobe_ipmodify_ops. This triggers a WARN in
> __disarm_kprobe_ftrace() and may even cause use-after-free:
>
> Failed to disarm kprobe-ftrace at kernel_clone+0x0/0x3c0 (error -2)
> WARNING: CPU: 5 PID: 137 at kernel/kprobes.c:1135 __disarm_kprobe_ftrace.isra.21+0xcf/0xe0
> Modules linked in: testKprobe_007(-)
> CPU: 5 PID: 137 Comm: rmmod Not tainted 6.1.0-rc4-dirty #18
> [...]
> Call Trace:
> <TASK>
> __disable_kprobe+0xcd/0xe0
> __unregister_kprobe_top+0x12/0x150
> ? mutex_lock+0xe/0x30
> unregister_kprobes.part.23+0x31/0xa0
> unregister_kprobe+0x32/0x40
> __x64_sys_delete_module+0x15e/0x260
> ? do_user_addr_fault+0x2cd/0x6b0
> do_syscall_64+0x3a/0x90
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [...]
>
> For the kprobe-on-ftrace case, we keep the post_handler setting to
> identify this aggrprobe armed with kprobe_ipmodify_ops. This way we
> can disarm it correctly.
This looks good to me. Thanks!
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
>
> Fixes: 0bc11ed5ab60 ("kprobes: Allow kprobes coexist with livepatch")
> Reported-by: Zhao Gongyi <zhaogongyi@...wei.com>
> Suggested-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> Signed-off-by: Li Huafei <lihuafei1@...wei.com>
> ---
> kernel/kprobes.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index cd9f5a66a690..3050631e528d 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1766,7 +1766,13 @@ static int __unregister_kprobe_top(struct kprobe *p)
> if ((list_p != p) && (list_p->post_handler))
> goto noclean;
> }
> - ap->post_handler = NULL;
> + /*
> + * For the kprobe-on-ftrace case, we keep the
> + * post_handler setting to identify this aggrprobe
> + * armed with kprobe_ipmodify_ops.
> + */
> + if (!kprobe_ftrace(ap))
> + ap->post_handler = NULL;
> }
> noclean:
> /*
> --
> 2.17.1
>
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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