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Benjamin Coddington 1e9c75fb9c mnt: fix __detach_mounts infinite loop 
Since commit ff17fa561a ("d_invalidate(): unhash immediately")
immediately unhashes the dentry, we'll never return the mountpoint in
lookup_mountpoint(), which can lead to an unbreakable loop in
d_invalidate().

I have reports of NFS clients getting into this condition after the server
removes an export of an existing mount created through follow_automount(),
but I suspect there are various other ways to produce this problem if we
hunt down users of d_invalidate().  For example, it is possible to get into
this state by using XFS' d_invalidate() call in xfs_vn_unlink():

truncate -s 100m img{1,2}

mkfs.xfs -q -n version=ci img1
mkfs.xfs -q -n version=ci img2

mkdir -p /mnt/xfs
mount img1 /mnt/xfs

mkdir /mnt/xfs/sub1
mount img2 /mnt/xfs/sub1

cat > /mnt/xfs/sub1/foo &
umount -l /mnt/xfs/sub1
mount img2 /mnt/xfs/sub1

mount --make-private /mnt/xfs

mkdir /mnt/xfs/sub2
mount --move /mnt/xfs/sub1 /mnt/xfs/sub2
rmdir /mnt/xfs/sub1

Fix this by moving the check for an unlinked dentry out of the
detach_mounts() path.

Fixes: ff17fa561a ("d_invalidate(): unhash immediately")
Cc: stable@vger.kernel.org
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2018-11-12 01:02:34 -06:00
arch
block
certs
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Documentation This pull request contains updates for UBIFS: 2018-11-04 14:46:04 -08:00
drivers This pull request contains updates for UBIFS: 2018-11-04 14:46:04 -08:00
firmware
fs mnt: fix __detach_mounts infinite loop 2018-11-12 01:02:34 -06:00
include NFS client bugfixes for Linux 4.20 2018-11-04 08:20:09 -08:00
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kernel userns: also map extents in the reverse map to kernel IDs 2018-11-07 23:51:16 -06:00
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Makefile Linux 4.20-rc1 2018-11-04 15:37:52 -08:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.