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Date:   Tue, 15 Oct 2019 19:40:34 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     "Pavel V. Panteleev" <panteleev_p@mcst.ru>
Cc:     linux-fsdevel@vger.kernel.org
Subject: Re: copy_mount_options() problem
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References: <5DA60B3E.5080303@mcst.ru>
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On Tue, Oct 15, 2019 at 09:09:02PM +0300, Pavel V. Panteleev wrote:
> Hello,
> 
> copy_mount_options() checks that data doesn't cross TASK_SIZE boundary. It's
> not correct. Really it should check USER_DS boudary, because some archs have
> TASK_SIZE not equal to USER_DS. In this case (USER_DS != TASK_SIZE)
> exact_copy_from_user() will stop on access_ok() check, if data cross
> USER_DS, but doesn't cross TASK_SIZE.

Details of the call chain, please.