linux-kernel - Re: [PATCH v1 3/5] mm: Fix failure to unmap pte on highmem systems

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: <27f2ad91-2507-a58c-2fb7-211c7f90bbdb@arm.com>
Date:   Thu, 11 May 2023 14:14:35 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        SeongJae Park <sj@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        damon@...ts.linux.dev
Subject: Re: [PATCH v1 3/5] mm: Fix failure to unmap pte on highmem systems

My appologies for the noise: A blank line between Cc and Subject has broken the
subject and grouping in lore.

Please Ignore this, I will resend.


On 11/05/2023 13:58, Ryan Roberts wrote:
> The loser of a race to service a pte for a device private entry in the
> swap path previously unlocked the ptl, but failed to unmap the pte. This
> only affects highmem systems since unmapping a pte is a noop on
> non-highmem systems.
> 
> Fixes: 16ce101db85d ("mm/memory.c: fix race when faulting a device private page")
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  mm/memory.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index f69fbc251198..ed429e20a1bb 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3728,10 +3728,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>  			vmf->page = pfn_swap_entry_to_page(entry);
>  			vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
>  					vmf->address, &vmf->ptl);
> -			if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
> -				spin_unlock(vmf->ptl);
> -				goto out;
> -			}
> +			if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte)))
> +				goto unlock;
>  
>  			/*
>  			 * Get a page reference while we know the page can't be