linux-kernel - Re: [RFC PATCH v3 2/6] [PATCH 2/6] mm: add merging after mremap resize

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: <20220520134124.6glbfzhrgzutfor6@box.shutemov.name>
Date:   Fri, 20 May 2022 16:41:24 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Jakub Matěna <matenajakub@...il.com>
Cc:     linux-mm@...ck.org, patches@...ts.linux.dev,
        linux-kernel@...r.kernel.org, vbabka@...e.cz, mhocko@...nel.org,
        mgorman@...hsingularity.net, willy@...radead.org,
        liam.howlett@...cle.com, hughd@...gle.com, riel@...riel.com,
        rostedt@...dmis.org, peterz@...radead.org, david@...hat.com
Subject: Re: [RFC PATCH v3 2/6] [PATCH 2/6] mm: add merging after mremap
 resize

On Mon, May 16, 2022 at 02:54:01PM +0200, Jakub Matěna wrote:
> When mremap call results in expansion, it might be possible to merge the
> VMA with the next VMA which might become adjacent. This patch adds
> vma_merge call after the expansion is done to try and merge.
> 
> Signed-off-by: Jakub Matěna <matenajakub@...il.com>
> ---
>  mm/mremap.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 303d3290b938..75cda854ec58 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -9,6 +9,7 @@
>   */
>  
>  #include <linux/mm.h>
> +#include <linux/mm_inline.h>
>  #include <linux/hugetlb.h>
>  #include <linux/shm.h>
>  #include <linux/ksm.h>
> @@ -1022,8 +1023,10 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
>  				}
>  			}
>  
> -			if (vma_adjust(vma, vma->vm_start, addr + new_len,
> -				       vma->vm_pgoff, NULL)) {
> +			if (!vma_merge(mm, vma, addr + old_len, addr + new_len,
> +					vma->vm_flags, vma->anon_vma, vma->vm_file,
> +					vma->vm_pgoff + (old_len >> PAGE_SHIFT), vma_policy(vma),
> +					vma->vm_userfaultfd_ctx, anon_vma_name(vma))) {

Hm. Don't you need to update 'vma' with result of vma_merge()?

'vma' is used below the point and IIUC it can be use-after-free.

-- 
 Kirill A. Shutemov