linux-kernel - Re: [PATCH v5 1/4] mm/debug_vm_pgtable: remove pte entry from the page table

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] [day] [month] [year] [list]

Date:   Wed, 2 Feb 2022 11:55:30 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Pasha Tatashin <pasha.tatashin@...een.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, rientjes@...gle.com, pjt@...gle.com,
        weixugc@...gle.com, gthelen@...gle.com, mingo@...hat.com,
        will@...nel.org, rppt@...nel.org, dave.hansen@...ux.intel.com,
        hpa@...or.com, aneesh.kumar@...ux.ibm.com, jirislaby@...nel.org,
        songmuchun@...edance.com, qydwhotmail@...il.com, hughd@...gle.com,
        ziy@...dia.com
Subject: Re: [PATCH v5 1/4] mm/debug_vm_pgtable: remove pte entry from the
 page table



On 2/1/22 2:02 AM, Pasha Tatashin wrote:
> The pte entry that is used in pte_advanced_tests() is never removed from
> the page table at the end of the test.
> 
> The issue is detected by page_table_check, to repro compile kernel with
> the following configs:
> 
> CONFIG_DEBUG_VM_PGTABLE=y
> CONFIG_PAGE_TABLE_CHECK=y
> CONFIG_PAGE_TABLE_CHECK_ENFORCED=y
> 
> During the boot the following BUG is printed:
> 
> [    2.262821] debug_vm_pgtable: [debug_vm_pgtable         ]: Validating
>                architecture page table helpers
> [    2.276826] ------------[ cut here ]------------
> [    2.280426] kernel BUG at mm/page_table_check.c:162!
> [    2.284118] invalid opcode: 0000 [#1] PREEMPT SMP PTI
> [    2.287787] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
>                5.16.0-11413-g2c271fe77d52 #3
> [    2.293226] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>                BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org
>                04/01/2014
> ...
> 
> The entry should be properly removed from the page table before the page
> is released to the free list.
> 
> Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers")
> Cc: stable@...r.kernel.org # 5.9+

Not sure marking stable is necessary here.

> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> Reviewed-by: Zi Yan <ziy@...dia.com>
> Tested-by: Zi Yan <ziy@...dia.com>
> Acked-by: David Rientjes <rientjes@...gle.com>

Dont see any problems on arm64. Although it would be great to run this
on all enabled platforms.

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>

> ---
>  mm/debug_vm_pgtable.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index a7ac97c76762..db2abd9e415b 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -171,6 +171,8 @@ static void __init pte_advanced_tests(struct pgtable_debug_args *args)
>  	ptep_test_and_clear_young(args->vma, args->vaddr, args->ptep);
>  	pte = ptep_get(args->ptep);
>  	WARN_ON(pte_young(pte));
> +
> +	ptep_get_and_clear_full(args->mm, args->vaddr, args->ptep, 1);
>  }
>  
>  static void __init pte_savedwrite_tests(struct pgtable_debug_args *args)
>