linux-kernel - Re: [PATCH stable 6.6] lib/buildid: Handle memfd_secret() files in build_id

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Message-ID: <CAEf4BzZAT_w+=7marwFgMg0i258KJFDnwrwnfwAjZ1DRX52ojA@mail.gmail.com>
Date: Wed, 12 Mar 2025 11:43:12 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Chen Linxuan <chenlinxuan@...pin.org>
Cc: Greg KH <gregkh@...uxfoundation.org>, Jiri Olsa <jolsa@...nel.org>, 
	Andrii Nakryiko <andrii@...nel.org>, Sasha Levin <sashal@...nel.org>, Jann Horn <jannh@...gle.com>, 
	Alexey Dobriyan <adobriyan@...il.com>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, 
	Alexei Starovoitov <ast@...nel.org>, stable@...r.kernel.org, 
	Eduard Zingerman <eddyz87@...il.com>, linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH stable 6.6] lib/buildid: Handle memfd_secret() files in build_id_parse()

On Tue, Mar 11, 2025 at 8:03 PM Chen Linxuan <chenlinxuan@...pin.org> wrote:
>
> Greg KH <gregkh@...uxfoundation.org> 于2025年3月11日周二 19:14写道：
> >
> > On Tue, Mar 11, 2025 at 06:05:55PM +0800, Chen Linxuan wrote:
> > > Backport of a similar change from commit 5ac9b4e935df ("lib/buildid:
> > > Handle memfd_secret() files in build_id_parse()") to address an issue
> > > where accessing secret memfd contents through build_id_parse() would
> > > trigger faults.
> > >
> > > Original report and repro can be found in [0].
> > >
> > >   [0] https://lore.kernel.org/bpf/ZwyG8Uro%2FSyTXAni@ly-workstation/
> > >
> > > This repro will cause BUG: unable to handle kernel paging request in
> > > build_id_parse in 5.15/6.1/6.6.
> > >
> > > Some other discussions can be found in [1].
> > >
> > >   [1] https://lore.kernel.org/bpf/20241104175256.2327164-1-jolsa@kernel.org/T/#u
> > >
> > > Cc: stable@...r.kernel.org
> > > Fixes: 88a16a130933 ("perf: Add build id data in mmap2 event")
> > > Signed-off-by: Chen Linxuan <chenlinxuan@...pin.org>
> >
> > You dropped all the original signed-off-by and changelog text.  Just
>
> The original commit is based on commit de3ec364c3c3 ("lib/buildid: add
> single folio-based file reader abstraction"). `git cherry-pick` result lots of
> conflicts. So I rewrite same logic on old code.
>

Yep, for the purpose of fixing the issue, I wouldn't try to backport
my folio-based changes to lib/buildid. What you are doing here (an
equivalent direct check for secretmem) makes sense to me.

Acked-by: Andrii Nakryiko <andrii@...nel.org>

> > provide a backport with all of the original information, and then if you
> > had to do something "different", put that in the signed-off-by area.
> > THere are loads of examples on the list for how that was done.
>
> Do you means that I should:
>
> 1. Run git cherry-pick 5ac9b4e935df on stable branches;
> 2. Resolve conflicts by drop all changes then apply changes
>    as I send in this email;
> 3. Note why content of this patch is different from the original
>    one after original signed-off-by area, but before the --- separator.
>
> I am not familiar with contributing to stable kernel tree.
> Sorry for bothering.
>
> >
> > thanks,
> >
> > greg k-h
> >
> >