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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Carsten Jacobi <jacobi@de.ibm.com>,
        David Howells <dhowells@redhat.com>,
        Marc Dionne <marc.dionne@auristor.com>,
        Jonathan Billings <jsbillings@jsbillings.org>,
        Todd DeSantis <atd@us.ibm.com>
Subject: [PATCH 4.19 31/84] afs: Fix missing cell comparison in afs_test_super()
Date:   Fri, 17 Jan 2020 00:18:05 +0100
Message-Id: <20200116231717.380111014@linuxfoundation.org>
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From: David Howells <dhowells@redhat.com>

commit 106bc79843c3c6f4f00753d1f46e54e815f99377 upstream.

Fix missing cell comparison in afs_test_super().  Without this, any pair
volumes that have the same volume ID will share a superblock, no matter the
cell, unless they're in different network namespaces.

Normally, most users will only deal with a single cell and so they won't
see this.  Even if they do look into a second cell, they won't see a
problem unless they happen to hit a volume with the same ID as one they've
already got mounted.

Before the patch:

    # ls /afs/grand.central.org/archive
    linuxdev/  mailman/  moin/  mysql/  pipermail/  stage/  twiki/
    # ls /afs/kth.se/
    linuxdev/  mailman/  moin/  mysql/  pipermail/  stage/  twiki/
    # cat /proc/mounts | grep afs
    none /afs afs rw,relatime,dyn,autocell 0 0
    #grand.central.org:root.cell /afs/grand.central.org afs ro,relatime 0 0
    #grand.central.org:root.archive /afs/grand.central.org/archive afs ro,relatime 0 0
    #grand.central.org:root.archive /afs/kth.se afs ro,relatime 0 0

After the patch:

    # ls /afs/grand.central.org/archive
    linuxdev/  mailman/  moin/  mysql/  pipermail/  stage/  twiki/
    # ls /afs/kth.se/
    admin/        common/  install/  OldFiles/  service/  system/
    bakrestores/  home/    misc/     pkg/       src/      wsadmin/
    # cat /proc/mounts | grep afs
    none /afs afs rw,relatime,dyn,autocell 0 0
    #grand.central.org:root.cell /afs/grand.central.org afs ro,relatime 0 0
    #grand.central.org:root.archive /afs/grand.central.org/archive afs ro,relatime 0 0
    #kth.se:root.cell /afs/kth.se afs ro,relatime 0 0

Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Carsten Jacobi <jacobi@de.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Tested-by: Jonathan Billings <jsbillings@jsbillings.org>
cc: Todd DeSantis <atd@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/afs/super.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -356,6 +356,7 @@ static int afs_test_super(struct super_b
 	return (as->net_ns == as1->net_ns &&
 		as->volume &&
 		as->volume->vid == as1->volume->vid &&
+		as->cell == as1->cell &&
 		!as->dyn_root);
 }