Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   B K Karthik <bkkarthik@pesu.pes.edu>
Date:   Wed, 15 Jul 2020 08:50:18 -0400
To:     Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] fs: block_dev.c: fix WARNING in submit_bio_check
Message-ID: <20200715125018.mjj6sj5uibd5s67b@pesu-pes-edu>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
        protocol="application/pgp-signature"; boundary="lpn6rsynz3x3gxmk"
Content-Disposition: inline
User-Agent: NeoMutt/20180716
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


--lpn6rsynz3x3gxmk
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

duplicating the logic in blkdev_get_by_path to
blkdev_get_by_dev to avoid a user-triggerable WARN
trying to write to a read-only block device.

blkdev_get_by_path() looks at
((mode & FMODE_WRITE) && bdev_read_only(bdev)) to check for write permissio=
ns.

A user-triggerable WARN can be avoided by doing the same with bdev_get_by_d=
ev.

Reported-by: syzbot+4c50ac32e5b10e4133e1@syzkaller.appspotmail.com
Signed-off-by: B K Karthik <karthik.bk2000@live.com>
---
 fs/block_dev.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 64c4fe8181f2..472e3b046406 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1796,6 +1796,11 @@ struct block_device *blkdev_get_by_dev(dev_t dev, fm=
ode_t mode, void *holder)
 	if (err)
 		return ERR_PTR(err);
=20
+	if ((mode & FMODE_WRITE) && bdev_read_only(bdev)) {
+		blkdev_put(bdev, mode);
+		return ERR_PTR(-EACCES);
+	}
+
 	return bdev;
 }
 EXPORT_SYMBOL(blkdev_get_by_dev);
--=20
2.20.1


--lpn6rsynz3x3gxmk
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=Pl6p
-----END PGP SIGNATURE-----

--lpn6rsynz3x3gxmk--