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

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Message-ID: <87zjavehsx.fsf@openvz.org>
Date:	Wed, 10 Dec 2014 16:49:18 +0300
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	ext4 development <linux-ext4@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>,
	Al Viro <viro@...IV.linux.org.uk>
Subject: Re: [PATCH] fs: make generic_block_fiemap sig-tolerant PING2...


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

Dmitry Monakhov <dmonakhov@...nvz.org> writes:
> Andrew can you please get this patch. IMHO it is simple and clean.
> BTW:
>
>> __generic_block_fiemap may spin very long time for large sparse files.
>>
>> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
>> ---
>>  fs/ioctl.c |    5 +++++
>>  1 files changed, 5 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/ioctl.c b/fs/ioctl.c
>> index 8ac3fad..6fbeb68 100644
>> --- 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);
>>  
>>  	/* If ret is 1 then we just hit the end of the extent array */
>> -- 
>> 1.7.1

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