linux-kernel - Re: [git pull] vfs part 2

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Message-id: <5587F943.3040006@samsung.com>
Date:	Mon, 22 Jun 2015 15:02:11 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [git pull] vfs part 2

On 06/22/2015 12:12 AM, Al Viro wrote:
> On Thu, Apr 23, 2015 at 01:16:15PM +0300, Andrey Ryabinin wrote:
>> This change caused following:
> 
>> This could happen when p9pdu_readf() changes 'count' to some value > iov_iter_count(from):
>>
>> p9_client_write():
>> <...>
>> 		int count = iov_iter_count(from);
>> <...>
>> 		*err = p9pdu_readf(req->rc, clnt->proto_version, "d", &count);
>> <...>
>> 		iov_iter_advance(from, count);
> 
> *blink*
> 
> That's a bug, all right, but I would love to see how you trigger it.
> It would require server to respond to "write that many bytes" with "OK,
> <greater number> bytes written".  We certainly need to cope with that
> (we can't trust the server to be sane), but if that's what is going on,
> you've got a server bug as well.
> 
> Could you check if the patch below triggers WARN_ON() in it on your
> reproducer?  p9_client_read() has a similar issue as well...
> 

I've tried something like your patch before to check the read side
and I haven't seen anything before and don't see it right now.
Though, this doesn't mean that there is no problem with read.
I mean that trinity hits this on write and may just not hit this on read.


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