linux-kernel - Re: [PATCH] fs: make generic_block

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Message-ID: <87egrwf1dd.fsf@openvz.org>
Date:	Fri, 19 Dec 2014 12:13:50 +0300
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	ext4 development <linux-ext4@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>,
	Al Viro <viro@...IV.linux.org.uk>,
	Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH] fs: make generic_block_fiemap sig-tolerant PING2...

Andrew Morton <akpm@...ux-foundation.org> writes:

> On Wed, 10 Dec 2014 16:49:18 +0300 Dmitry Monakhov <dmonakhov@...nvz.org> wrote:
>
>> 
>> Hello. Someone please take care of this patch.
>> 
>> W/o that patch unprivileged user may abuse system resources simply by spawning
>> wast number of unkilable busyloops (works on ext2/ext3):
>> 
>> truncate --size 1T test
>> for ((i=0;i<1024;i++))
>> do
>>        filefrag test > /dev/null &
>> done
>> 
>> >> --- a/fs/ioctl.c
>> >> +++ b/fs/ioctl.c
>> >> @@ -379,6 +379,11 @@ int __generic_block_fiemap(struct inode *inode,
>> >>  				past_eof = true;
>> >>  		}
>> >>  		cond_resched();
>> >> +		if (fatal_signal_pending(current)) {
>> >> +			ret = -EINTR;
>> >> +			break;
>> >> +		}
>> >> +
>> >>  	} while (1);
>> >>  
>
> Is FIEMAP documented anywhere (manpage)?  If so, that will need an
> update.
Yes you right. I just thought that it is assumed by default.
The only place I know is Documentation/filesystems/fiemap.txt
Please fold patch attached to original one.

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