linux-kernel - Re: [PATCH] mm: fix kernel BUG at mm/rmap.c:1017!

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: <201105291823.47082.nai.xia@gmail.com>
Date:	Sun, 29 May 2011 18:23:46 +0800
From:	Nai Xia <nai.xia@...il.com>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shaohua Li <shaohua.li@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: fix kernel BUG at mm/rmap.c:1017!

On Sunday 29 May 2011 04:17:04 Hugh Dickins wrote:
> I've hit the "address >= vma->vm_end" check in do_page_add_anon_rmap()
> just once.  The stack showed khugepaged allocation trying to compact
> pages: the call to page_add_anon_rmap() coming from remove_migration_pte().
> 
> That path holds anon_vma lock, but does not hold mmap_sem: it can
> therefore race with a split_vma(), and in commit 5f70b962ccc2 "mmap:
> avoid unnecessary anon_vma lock" we just took away the anon_vma lock
> protection when adjusting vma->vm_end.
> 
> I don't think that particular BUG_ON ever caught anything interesting,
> so better replace it by a comment, than reinstate the anon_vma locking.

Is there another racing between "vma->vm_pgoff = pgoff;" in 
vma_adjust() and linear_page_index() in __page_set_anon_rmap() ?


Nai Xia

> 
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> ---
>  mm/rmap.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> --- linux.orig/mm/rmap.c	2011-05-27 19:05:27.000000000 -0700
> +++ linux/mm/rmap.c	2011-05-27 20:07:44.601361236 -0700
> @@ -1014,7 +1014,7 @@ void do_page_add_anon_rmap(struct page *
>  		return;
>  
>  	VM_BUG_ON(!PageLocked(page));
> -	VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
> +	/* address might be in next vma when migration races vma_adjust */
>  	if (first)
>  		__page_set_anon_rmap(page, vma, address, exclusive);
>  	else
> @@ -1709,7 +1709,7 @@ void hugepage_add_anon_rmap(struct page
>  
>  	BUG_ON(!PageLocked(page));
>  	BUG_ON(!anon_vma);
> -	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
> +	/* address might be in next vma when migration races vma_adjust */
>  	first = atomic_inc_and_test(&page->_mapcount);
>  	if (first)
>  		__hugepage_set_anon_rmap(page, vma, address, 0);
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@...ck.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
> 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/