linux-kernel - Re: [PATCH v3 3/7] mm/mprotect: Replace can_modify_mm with can_modify

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Message-ID: <x5djrsgqvmk4gqnuxbsig77jwthjhlfcvtjtwxhopj6y54lil2@dfyavfeqf7ws>
Date: Mon, 19 Aug 2024 16:33:18 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Pedro Falcato <pedro.falcato@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Shuah Khan <shuah@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        jeffxu@...omium.org, oliver.sang@...el.com,
        torvalds@...ux-foundation.org, Michael Ellerman <mpe@...erman.id.au>,
        Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 3/7] mm/mprotect: Replace can_modify_mm with
 can_modify_vma

* Pedro Falcato <pedro.falcato@...il.com> [240816 20:19]:
> Avoid taking an extra trip down the mmap tree by checking the vmas
> directly. mprotect (per POSIX) tolerates partial failure.
> 
> Signed-off-by: Pedro Falcato <pedro.falcato@...il.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>

> ---
>  mm/mprotect.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 446f8e5f10d9..0c5d6d06107d 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -611,6 +611,9 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
>  	unsigned long charged = 0;
>  	int error;
>  
> +	if (!can_modify_vma(vma))
> +		return -EPERM;
> +
>  	if (newflags == oldflags) {
>  		*pprev = vma;
>  		return 0;
> @@ -769,15 +772,6 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
>  		}
>  	}
>  
> -	/*
> -	 * checking if memory is sealed.
> -	 * can_modify_mm assumes we have acquired the lock on MM.
> -	 */
> -	if (unlikely(!can_modify_mm(current->mm, start, end))) {
> -		error = -EPERM;
> -		goto out;
> -	}
> -
>  	prev = vma_prev(&vmi);
>  	if (start > vma->vm_start)
>  		prev = vma;
> 
> -- 
> 2.46.0
>