[v3,08/16] mm/mmap: Inline munmap operation in mmap_region()

Commit Message

Liam R. Howlett July 4, 2024, 6:27 p.m. UTC

From: "Liam R. Howlett" <[e-mail]>

mmap_region is already passed sanitized addr and len, so change the
call to do_vmi_munmap() to do_vmi_align_munmap() and inline the other
checks.

Signed-off-by: Liam R. Howlett <[e-mail]>
---
 mm/mmap.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

Comments

Lorenzo Stoakes July 5, 2024, 7:39 p.m. UTC | #1

On Thu, Jul 04, 2024 at 02:27:10PM GMT, Liam R. Howlett wrote:
> From: "Liam R. Howlett" <[e-mail]>
>
> mmap_region is already passed sanitized addr and len, so change the
> call to do_vmi_munmap() to do_vmi_align_munmap() and inline the other
> checks.
>
> Signed-off-by: Liam R. Howlett <[e-mail]>
> ---
>  mm/mmap.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 8d9be791997a..e9858ca8bbd4 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2937,12 +2937,20 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>  			return -ENOMEM;
>  	}
>
> -	/* Unmap any existing mapping in the area */

This feels like an important comment, I know 'find the first overlapping
VMA' below alludes to it but whenever I've read through this function this
comment has actually been quite useful to know what the intent is.

Could we reinstate it?

> -	error = do_vmi_munmap(&vmi, mm, addr, len, uf, false);
> -	if (error == -EPERM)
> -		return error;
> -	else if (error)
> -		return -ENOMEM;
> +
> +	if (unlikely(!can_modify_mm(mm, addr, end)))
> +		return -EPERM;
> +
> +	 /* arch_unmap() might do unmaps itself.  */
> +	arch_unmap(mm, addr, end);
> +
> +	/* Find the first overlapping VMA */
> +	vma = vma_find(&vmi, end);
> +	if (vma) {
> +		if (do_vmi_align_munmap(&vmi, vma, mm, addr, end, uf, false))
> +			return -ENOMEM;
> +		vma = NULL;
> +	}
>
>  	/*
>  	 * Private writable mapping: check memory availability
> --
> 2.43.0
>
>

Other than trivial point above, LGTM.

Reviewed-by: Lorenzo Stoakes <[e-mail]>

Liam R. Howlett July 5, 2024, 8 p.m. UTC | #2

* Lorenzo Stoakes <[e-mail]> [240705 15:40]:
> On Thu, Jul 04, 2024 at 02:27:10PM GMT, Liam R. Howlett wrote:
> > From: "Liam R. Howlett" <[e-mail]>
> >
> > mmap_region is already passed sanitized addr and len, so change the
> > call to do_vmi_munmap() to do_vmi_align_munmap() and inline the other
> > checks.
> >
> > Signed-off-by: Liam R. Howlett <[e-mail]>
> > ---
> >  mm/mmap.c | 20 ++++++++++++++------
> >  1 file changed, 14 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 8d9be791997a..e9858ca8bbd4 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -2937,12 +2937,20 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> >  			return -ENOMEM;
> >  	}
> >
> > -	/* Unmap any existing mapping in the area */
> 
> This feels like an important comment, I know 'find the first overlapping
> VMA' below alludes to it but whenever I've read through this function this
> comment has actually been quite useful to know what the intent is.
> 
> Could we reinstate it?

Ah, sure.  I am going to have to move it around and it sort of loses its
meaning a bit once we gather and complete it (and not actually zero the
tree)..  I'll try to keep it with the correct code block.

> 
> > -	error = do_vmi_munmap(&vmi, mm, addr, len, uf, false);
> > -	if (error == -EPERM)
> > -		return error;
> > -	else if (error)
> > -		return -ENOMEM;
> > +
> > +	if (unlikely(!can_modify_mm(mm, addr, end)))
> > +		return -EPERM;
> > +
> > +	 /* arch_unmap() might do unmaps itself.  */
> > +	arch_unmap(mm, addr, end);
> > +
> > +	/* Find the first overlapping VMA */
> > +	vma = vma_find(&vmi, end);
> > +	if (vma) {
> > +		if (do_vmi_align_munmap(&vmi, vma, mm, addr, end, uf, false))
> > +			return -ENOMEM;
> > +		vma = NULL;
> > +	}
> >
> >  	/*
> >  	 * Private writable mapping: check memory availability
> > --
> > 2.43.0
> >
> >
> 
> Other than trivial point above, LGTM.
> 
> Reviewed-by: Lorenzo Stoakes <[e-mail]>

Thanks!

Patch

diff --git a/mm/mmap.c b/mm/mmap.c
index 8d9be791997a..e9858ca8bbd4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2937,12 +2937,20 @@  unsigned long mmap_region(struct file *file, unsigned long addr,
 			return -ENOMEM;
 	}
 
-	/* Unmap any existing mapping in the area */
-	error = do_vmi_munmap(&vmi, mm, addr, len, uf, false);
-	if (error == -EPERM)
-		return error;
-	else if (error)
-		return -ENOMEM;
+
+	if (unlikely(!can_modify_mm(mm, addr, end)))
+		return -EPERM;
+
+	 /* arch_unmap() might do unmaps itself.  */
+	arch_unmap(mm, addr, end);
+
+	/* Find the first overlapping VMA */
+	vma = vma_find(&vmi, end);
+	if (vma) {
+		if (do_vmi_align_munmap(&vmi, vma, mm, addr, end, uf, false))
+			return -ENOMEM;
+		vma = NULL;
+	}
 
 	/*
 	 * Private writable mapping: check memory availability