linux-kernel - Re: Add Morton,Peter and David for discussion//Re: [PATCH -next] uprobes: fix two zero old_folio bugs in __replace

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Message-ID: <196fc7d8-30a8-439a-89bd-57353fd98df8@redhat.com>
Date: Thu, 20 Feb 2025 09:38:17 +0100
From: David Hildenbrand <david@...hat.com>
To: Tong Tiangen <tongtiangen@...wei.com>, Oleg Nesterov <oleg@...hat.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 "Liang, Kan" <kan.liang@...ux.intel.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Peter Xu <peterx@...hat.com>,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, bpf@...r.kernel.org,
 wangkefeng.wang@...wei.com, linux-mm <linux-mm@...ck.org>
Subject: Re: Add Morton,Peter and David for discussion//Re: [PATCH -next]
 uprobes: fix two zero old_folio bugs in __replace_page()

On 20.02.25 03:31, Tong Tiangen wrote:
> 
> 
> 在 2025/2/20 0:12, David Hildenbrand 写道:
>> On 19.02.25 16:22, Oleg Nesterov wrote:
>>> On 02/18, Tong Tiangen wrote:
>>>>
>>>> OK, Before your rewrite last merged, How about i change the solution to
>>>> just reject them immediately after get_user_page_vma_remote()？
>>>
>>> I agree, uprobe_write_opcode() should simply fail if
>>> is_zero_page(old_page).
>>
>> Yes. That's currently only syzkaller that triggers it, not some sane use
>> case.
> 
> OK, change as follows:
> 
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -506,6 +506,12 @@ int uprobe_write_opcode(struct arch_uprobe
> *auprobe, struct mm_struct *mm,
>           if (ret <= 0)
>                   goto put_old;
> 
> +       if (WARN(is_zero_page(old_page),

This can likely be triggered by user space, so do not use WARN.

-- 
Cheers,

David / dhildenb