[PATCH] lib/buildid: Handle memfd_secret() files in build_id_parse()

[PATCH] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Chen Linxuan]

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@vger.kernel.org
Fixes: 88a16a130933 ("perf: Add build id data in mmap2 event")
Signed-off-by: Chen Linxuan <chenlinxuan@deepin.org>
---
 lib/buildid.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/buildid.c b/lib/buildid.c
index 9fc46366597e..b78d119ed1f7 100644
--- 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 */
-- 
2.48.1

Re: [PATCH] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Jiri Olsa]

On Thu, Mar 06, 2025 at 01:06:58PM +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.

hi,
so this patch is meant for one of 5.15/6.1/6.6?

if so you need to send it separately and add that to the subject,
please check Documentation/process/stable-kernel-rules.rst

and you can check other stable kernel patches on the mailing list
like [1][2]

thanks,
jirka


[1] https://lore.kernel.org/bpf/20241206153403.273068-2-daniel@iogearbox.net/
[2] https://lore.kernel.org/bpf/20241104175256.2327164-3-jolsa@kernel.org/

> 
> Some other discussions can be found in [1].
> 
>   [1] https://lore.kernel.org/bpf/20241104175256.2327164-1-jolsa@kernel.org/T/#u
> 
> Cc: stable@vger.kernel.org
> Fixes: 88a16a130933 ("perf: Add build id data in mmap2 event")
> Signed-off-by: Chen Linxuan <chenlinxuan@deepin.org>
> ---
>  lib/buildid.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/lib/buildid.c b/lib/buildid.c
> index 9fc46366597e..b78d119ed1f7 100644
> --- 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 */
> -- 
> 2.48.1
> 

Re: [PATCH] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Andrew Morton]

On Thu,  6 Mar 2025 13:06:58 +0800 Chen Linxuan <chenlinxuan@deepin.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.

Re: [PATCH] lib/buildid: Handle memfd_secret() files in build_id_parse()

[Chen Linxuan]

On Thu, Mar 06, 2025 at 03:08:11PM -0800, Andrew Morton wrote:
> On Thu,  6 Mar 2025 13:06:58 +0800 Chen Linxuan <chenlinxuan@deepin.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.

stable/linux-6.13.y and stable/linux-6.12.y has commit 5ac9b4e935df
("lib/buildid: Handle memfd_secret() files in build_id_parse()").

stable/linux-5.10.y and stable/linux-5.4.y do not have memfd_secret(2) feature,
so this patch is not needed.

> 
>