linux-kernel - Re: [PATCH] Fix sync. in inode_has_no

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Message-ID: <c4f0d66f-7cad-c3b4-79a6-ced14b9c7cc8@tu-dortmund.de>
Date:   Fri, 7 Dec 2018 11:24:47 +0100
From:   Alexander Lochmann <alexander.lochmann@...dortmund.de>
To:     Jan Kara <jack@...e.cz>
Cc:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Horst Schirmeier <horst.schirmeier@...dortmund.de>,
        linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH] Fix sync. in inode_has_no_xattr()

Am 05.12.18 um 16:32 schrieb Jan Kara:
> 
> Thinking more about this I'm not sure if this is actually the right
> solution. Because for example the write(2) can set S_NOSEC flag wrongly
> when it would race with chmod adding SUID bit. So probably we rather need
> to acquire i_rwsem in blkdev_write_iter() if file does not have S_NOSEC set
> (we don't want to acquire it unconditionally as that would heavily impact
> scalability of block device writes).
> 
> 								Honza
> 
Trying to implement your suggestion, I'm not sure which inode to use:
In blkdev_write_iter() there is the "bd_inode = bdev_file_inode(file)".
file_remove_privs() uses "inode = file_inode(file)" as a parameter for
inode_has_no_xattr().
So, do file->f_mapping->host and f->f_inode refer to the identical inode?

- Alex

-- 
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