linux-kernel - Re: [PATCH hotfix 6.12 2/8] mm: unconditionally close VMAs on error

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 for Android: free password hash cracker in your pocket

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

Message-ID: <CAG48ez3-ZcWzf5at25PTxcB0FVUCQR5OqjPpFKKgW=r3NTQmgg@mail.gmail.com>
Date: Tue, 22 Oct 2024 23:15:10 +0200
From: Jann Horn <jannh@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH hotfix 6.12 2/8] mm: unconditionally close VMAs on error

On Tue, Oct 22, 2024 at 10:41 PM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
> Incorrect invocation of VMA callbacks when the VMA is no longer in a
> consistent state is bug prone and risky to perform.
>
> With regards to the important vm_ops->close() callback We have gone to
> great lengths to try to track whether or not we ought to close VMAs.
>
> Rather than doing so and risking making a mistake somewhere, instead
> unconditionally close and reset vma->vm_ops to an empty dummy operations
> set with a NULL .close operator.
>
> We introduce a new function to do so - vma_close() - and simplify existing
> vms logic which tracked whether we needed to close or not.
>
> This simplifies the logic, avoids incorrect double-calling of the .close()
> callback and allows us to update error paths to simply call vma_close()
> unconditionally - making VMA closure idempotent.
>
> Reported-by: Jann Horn <jannh@...gle.com>
> Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
> Cc: stable <stable@...nel.org>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

Reviewed-by: Jann Horn <jannh@...gle.com>

[...]
> diff --git a/mm/vma.h b/mm/vma.h
> index 55457cb68200..75558b5e9c8c 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -42,7 +42,6 @@ struct vma_munmap_struct {
>         int vma_count;                  /* Number of vmas that will be removed */
>         bool unlock;                    /* Unlock after the munmap */
>         bool clear_ptes;                /* If there are outstanding PTE to be cleared */
> -       bool closed_vm_ops;             /* call_mmap() was encountered, so vmas may be closed */
>         /* 1 byte hole */

nit: outdated comment, this hole is 2 bytes now



>         unsigned long nr_pages;         /* Number of pages being removed */
>         unsigned long locked_vm;        /* Number of locked pages */