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To:     Jan Kara <jack@suse.cz>
Cc:     viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Horst Schirmeier <horst.schirmeier@tu-dortmund.de>,
        linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
References: <13eaa1c6-def5-afad-89eb-6f149db90684@tu-dortmund.de>
 <20181205153254.GD30615@quack2.suse.cz>
From:   Alexander Lochmann <alexander.lochmann@tu-dortmund.de>
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Subject: Re: [PATCH] Fix sync. in inode_has_no_xattr()
Message-ID: <c4f0d66f-7cad-c3b4-79a6-ced14b9c7cc8@tu-dortmund.de>
Date:   Fri, 7 Dec 2018 11:24:47 +0100
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From: Alexander Lochmann <alexander.lochmann@tu-dortmund.de>
To: Jan Kara <jack@suse.cz>
Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
 linux-kernel@vger.kernel.org,
 Horst Schirmeier <horst.schirmeier@tu-dortmund.de>,
 linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Message-ID: <c4f0d66f-7cad-c3b4-79a6-ced14b9c7cc8@tu-dortmund.de>
Subject: Re: [PATCH] Fix sync. in inode_has_no_xattr()
References: <13eaa1c6-def5-afad-89eb-6f149db90684@tu-dortmund.de>
 <20181205153254.GD30615@quack2.suse.cz>
In-Reply-To: <20181205153254.GD30615@quack2.suse.cz>

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Am 05.12.18 um 16:32 schrieb Jan Kara:
>=20
> 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 ne=
ed
> 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 impa=
ct
> scalability of block device writes).
>=20
> 								Honza
>=20
Trying to implement your suggestion, I'm not sure which inode to use:
In blkdev_write_iter() there is the "bd_inode =3D bdev_file_inode(file)".=

file_remove_privs() uses "inode =3D 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

--=20
Technische Universit=C3=A4t Dortmund
Alexander Lochmann                PGP key: 0xBC3EF6FD
Otto-Hahn-Str. 16                 phone:  +49.231.7556141
D-44227 Dortmund                  fax:    +49.231.7556116
http://ess.cs.tu-dortmund.de/Staff/al


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