linux-kernel - Re: [PATCH v3 03/16] mm/mmap: Introduce vmi_complete_munmap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6f082ff6-78bf-471a-be6d-857209d07726@lucifer.local>
Date: Fri, 5 Jul 2024 18:39:01 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Matthew Wilcox <willy@...radead.org>,
        sidhartha.kumar@...cle.com, "Paul E . McKenney" <paulmck@...nel.org>,
        Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>,
        linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 03/16] mm/mmap: Introduce vmi_complete_munmap_vmas()

On Thu, Jul 04, 2024 at 02:27:05PM GMT, Liam R. Howlett wrote:
> Extract all necessary operations that need to be completed after the vma
> maple tree is updated from a munmap() operation.  Extracting this makes
> the later patch in the series easier to understand.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>  mm/mmap.c | 79 +++++++++++++++++++++++++++++++++++++------------------
>  1 file changed, 53 insertions(+), 26 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index d572e1ff8255..411798f46932 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2605,6 +2605,56 @@ static inline void abort_munmap_vmas(struct ma_state *mas_detach)
>  	__mt_destroy(mas_detach->tree);
>  }
>
> +/*
> + * vmi_complete_munmap_vmas() - Finish the munmap() operation
> + * @vmi: The vma iterator
> + * @start: The start address
> + * @end: The end address
> + * @unlock: Unlock the mm or not
> + * @mas_detach: them maple state of the detached vma maple tree
> + * @locked_vm: The locked_vm count in the detached vmas
> + *
> + * This function updates the mm_struct, unmaps the region, frees the resources
> + * used for the munmap() and may downgrade the lock - if requested.  Everything
> + * needed to be done once the vma maple tree is updated.
> + */
> +static void
> +vmi_complete_munmap_vmas(struct vma_iterator *vmi, struct vm_area_struct *vma,
> +		struct mm_struct *mm, unsigned long start,
> +		unsigned long end, bool unlock, struct ma_state *mas_detach,
> +		unsigned long locked_vm)
> +{
> +	struct vm_area_struct *prev, *next;
> +	int count;
> +
> +	count = mas_detach->index + 1;
> +	mm->map_count -= count;
> +	mm->locked_vm -= locked_vm;
> +	if (unlock)
> +		mmap_write_downgrade(mm);
> +
> +	prev = vma_iter_prev_range(vmi);
> +	next = vma_next(vmi);
> +	if (next)
> +		vma_iter_prev_range(vmi);
> +
> +	/*
> +	 * We can free page tables without write-locking mmap_lock because VMAs
> +	 * were isolated before we downgraded mmap_lock.
> +	 */
> +	mas_set(mas_detach, 1);
> +	unmap_region(mm, mas_detach, vma, prev, next, start, end, count,
> +		     !unlock);
> +	/* Statistics and freeing VMAs */
> +	mas_set(mas_detach, 0);
> +	remove_mt(mm, mas_detach);
> +	validate_mm(mm);
> +	if (unlock)
> +		mmap_read_unlock(mm);
> +
> +	__mt_destroy(mas_detach->tree);
> +}
> +
>  /*
>   * do_vmi_align_munmap() - munmap the aligned region from @start to @end.
>   * @vmi: The vma iterator
> @@ -2624,7 +2674,7 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  		    struct mm_struct *mm, unsigned long start,
>  		    unsigned long end, struct list_head *uf, bool unlock)
>  {
> -	struct vm_area_struct *prev, *next = NULL;
> +	struct vm_area_struct *next = NULL;
>  	struct maple_tree mt_detach;
>  	int count = 0;
>  	int error = -ENOMEM;
> @@ -2728,31 +2778,8 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  		goto clear_tree_failed;
>
>  	/* Point of no return */
> -	mm->locked_vm -= locked_vm;
> -	mm->map_count -= count;
> -	if (unlock)
> -		mmap_write_downgrade(mm);
> -
> -	prev = vma_iter_prev_range(vmi);
> -	next = vma_next(vmi);
> -	if (next)
> -		vma_iter_prev_range(vmi);
> -
> -	/*
> -	 * We can free page tables without write-locking mmap_lock because VMAs
> -	 * were isolated before we downgraded mmap_lock.
> -	 */
> -	mas_set(&mas_detach, 1);
> -	unmap_region(mm, &mas_detach, vma, prev, next, start, end, count,
> -		     !unlock);
> -	/* Statistics and freeing VMAs */
> -	mas_set(&mas_detach, 0);
> -	remove_mt(mm, &mas_detach);
> -	validate_mm(mm);
> -	if (unlock)
> -		mmap_read_unlock(mm);
> -
> -	__mt_destroy(&mt_detach);
> +	vmi_complete_munmap_vmas(vmi, vma, mm, start, end, unlock, &mas_detach,
> +				 locked_vm);
>  	return 0;
>
>  clear_tree_failed:
> --
> 2.43.0
>
>

LGTM, feel free to add:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>