linux-kernel - Re: [PATCH 2/2] mm: vmalloc: Pass proper vm

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: <ee1e7036-ecdf-0f5b-f460-0d71b4a38dd7@linux.vnet.ibm.com>
Date:   Fri, 13 Apr 2018 17:31:49 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Chintan Pandya <cpandya@...eaurora.org>, vbabka@...e.cz,
        labbott@...hat.com, catalin.marinas@....com, hannes@...xchg.org,
        f.fainelli@...il.com, xieyisheng1@...wei.com,
        ard.biesheuvel@...aro.org, richard.weiyang@...il.com,
        byungchul.park@....com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] mm: vmalloc: Pass proper vm_start into debugobjects

On 04/13/2018 05:03 PM, Chintan Pandya wrote:
> Client can call vunmap with some intermediate 'addr'
> which may not be the start of the VM area. Entire
> unmap code works with vm->vm_start which is proper
> but debug object API is called with 'addr'. This
> could be a problem within debug objects.
> 
> Pass proper start address into debug object API.
> 
> Signed-off-by: Chintan Pandya <cpandya@...eaurora.org>
> ---
>  mm/vmalloc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 9ff21a1..28034c55 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1526,8 +1526,8 @@ static void __vunmap(const void *addr, int deallocate_pages)
>  		return;
>  	}
>  
> -	debug_check_no_locks_freed(addr, get_vm_area_size(area));
> -	debug_check_no_obj_freed(addr, get_vm_area_size(area));
> +	debug_check_no_locks_freed(area->addr, get_vm_area_size(area));
> +	debug_check_no_obj_freed(area->addr, get_vm_area_size(area));

This kind of makes sense to me but I am not sure. We also have another
instance of this inside the function vm_unmap_ram() where we call for
debug on locks without even finding the vmap_area first. But it is true
that in both these functions the vmap_area gets freed eventually. Hence
the entire mapping [va->va_start --> va->va_end] gets unmapped. Sounds
like these debug functions should have the entire range as argument.
But I am not sure and will seek Michal's input on this.