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From: Chao Yu <>
To: Jaegeuk Kim <>
Cc: <>,
	<>, <>
Subject: Re: [PATCH] f2fs: set deadline to drop expired inmem pages
Date: Fri, 13 Apr 2018 09:25:37 +0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 2018/4/13 9:04, Jaegeuk Kim wrote:
> On 04/10, Chao Yu wrote:
>> Hi Jaegeuk,
>> On 2018/4/8 16:13, Chao Yu wrote:
>>> f2fs doesn't allow abuse on atomic write class interface, so except
>>> limiting in-mem pages' total memory usage capacity, we need to limit
>>> start-commit time as well, otherwise we may run into infinite loop
>>> during foreground GC because target blocks in victim segment are
>>> belong to atomic opened file for long time.
>>> Now, we will check the condition with f2fs_balance_fs_bg in
>>> background threads, once if user doesn't commit data exceeding 30
>>> seconds, we will drop all cached data, so I expect it can keep our
>>> system running safely to prevent Dos attack.
>> Is it worth to add this patch to avoid abuse on atomic write interface by user?
> Hmm, hope to see a real problem first in this case.

I think this can be a more critical security leak instead of a potential issue
which we can wait for someone reporting that can be too late.

For example, user can simply write a huge file whose data spread in all f2fs
segments, once user open that file as atomic, foreground GC will suffer
deadloop, causing denying any further service of f2fs.


>> Thanks,
> .

  reply	other threads:[~2018-04-13  1:25 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-08  8:13 [PATCH] f2fs: set deadline to drop expired inmem pages Chao Yu
2018-04-10  7:38 ` Chao Yu
2018-04-13  1:04   ` Jaegeuk Kim
2018-04-13  1:25     ` Chao Yu [this message]
2018-04-13  4:05       ` Jaegeuk Kim
2018-04-13  6:08         ` Chao Yu
2018-04-16 20:16           ` Jaegeuk Kim
2018-04-17  6:44             ` Chao Yu
2018-04-17 11:45               ` Chao Yu
2018-04-18  4:14                 ` Jaegeuk Kim

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