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

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Message-Id: <20250306150811.a2a5fbf0919f06fb5f08178a@linux-foundation.org>
Date: Thu, 6 Mar 2025 15:08:11 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Chen Linxuan <chenlinxuan@...pin.org>
Cc: Sasha Levin <sashal@...nel.org>, Andrii Nakryiko <andrii@...nel.org>,
 Jiri Olsa <jolsa@...nel.org>, Jann Horn <jannh@...gle.com>, Alexei
 Starovoitov <ast@...nel.org>, Alexey Dobriyan <adobriyan@...il.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, stable@...r.kernel.org,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] lib/buildid: Handle memfd_secret() files in
 build_id_parse()

On Thu,  6 Mar 2025 13:06:58 +0800 Chen Linxuan <chenlinxuan@...pin.org> 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.
> 
> ...
>
> --- a/lib/buildid.c
> +++ b/lib/buildid.c
> @@ -157,6 +157,12 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
>  	if (!vma->vm_file)
>  		return -EINVAL;
>  
> +#ifdef CONFIG_SECRETMEM
> +	/* reject secretmem folios created with memfd_secret() */
> +	if (vma->vm_file->f_mapping->a_ops == &secretmem_aops)
> +		return -EFAULT;
> +#endif
> +
>  	page = find_get_page(vma->vm_file->f_mapping, 0);
>  	if (!page)
>  		return -EFAULT;	/* page not mapped */

Please redo this against a current kernel?  build_id_parse() has
changed a lot.