linux-kernel - Re: [stable] [PATCH] mm: prevent concurrent unmap_mapping

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]

Date:	Thu, 7 Jul 2011 16:55:47 -0700
From:	Greg KH <greg@...ah.com>
To:	Wengang Wang <wen.gang.wang@...cle.com>
Cc:	stable@...nel.org, greg.marsden@...cle.com, joe.jin@...cle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [stable] [PATCH] mm: prevent concurrent unmap_mapping_range() on
 the same inode --to stable

On Fri, Jun 24, 2011 at 03:02:08PM +0800, Wengang Wang wrote:
>         mainline commit 2aa15890f3c191326678f1bd68af61ec6b8753ec
> 
>     mm: prevent concurrent unmap_mapping_range() on the same inode
> 
>     Michael Leun reported that running parallel opens on a fuse filesystem
>     can trigger a "kernel BUG at mm/truncate.c:475"
> 
>     Gurudas Pai reported the same bug on NFS.
> 
>     The reason is, unmap_mapping_range() is not prepared for more than
>     one concurrent invocation per inode.  For example:
> 
>       thread1: going through a big range, stops in the middle of a vma and
>          stores the restart address in vm_truncate_count.
> 
>       thread2: comes in with a small (e.g. single page) unmap request on
>          the same vma, somewhere before restart_address, finds that the
>          vma was already unmapped up to the restart address and happily
>          returns without doing anything.
> 
>     Another scenario would be two big unmap requests, both having to
>     restart the unmapping and each one setting vm_truncate_count to its
>     own value.  This could go on forever without any of them being able to
>     finish.
> 
>     Truncate and hole punching already serialize with i_mutex.  Other
>     callers of unmap_mapping_range() do not, and it's difficult to get
>     i_mutex protection for all callers.  In particular ->d_revalidate(),
>     which calls invalidate_inode_pages2_range() in fuse, may be called
>     with or without i_mutex.
> 
>     This patch adds a new mutex to 'struct address_space' to prevent
>     running multiple concurrent unmap_mapping_range() on the same mapping.
> 
>     [ We'll hopefully get rid of all this with the upcoming mm
>       preemptibility series by Peter Zijlstra, the "mm: Remove i_mmap_mutex
>       lockbreak" patch in particular.  But that is for 2.6.39 ]
> 
> 
>     Adding this patch causes Kabi breakage.
> 
>     Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
>     Reported-by: Michael Leun <lkml20101129@...ton.leun.net>
>     Reported-by: Gurudas Pai <gurudas.pai@...cle.com>
>     Tested-by: Gurudas Pai <gurudas.pai@...cle.com>
>     Acked-by: Hugh Dickins <hughd@...gle.com>
>     Cc: stable@...nel.org
>     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
>     Signed-off-by: Wengang Wang <wen.gang.wang@...cle.com>

As this patch showed up in 2.6.39, I'm confused as to what you wanted me
to do with it, so I've dropped it from my queue.

greg k-h
--
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/