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Roger Pau Monne 462cdace79 xen: fix bio vec merging
The current test for bio vec merging is not fully accurate and can be
tricked into merging bios when certain grant combinations are used.
The result of these malicious bio merges is a bio that extends past
the memory page used by any of the originating bios.

Take into account the following scenario, where a guest creates two
grant references that point to the same mfn, ie: grant 1 -> mfn A,
grant 2 -> mfn A.

These references are then used in a PV block request, and mapped by
the backend domain, thus obtaining two different pfns that point to
the same mfn, pfn B -> mfn A, pfn C -> mfn A.

If those grants happen to be used in two consecutive sectors of a disk
IO operation becoming two different bios in the backend domain, the
checks in xen_biovec_phys_mergeable will succeed, because bfn1 == bfn2
(they both point to the same mfn). However due to the bio merging,
the backend domain will end up with a bio that expands past mfn A into
mfn A + 1.

Fix this by making sure the check in xen_biovec_phys_mergeable takes
into account the offset and the length of the bio, this basically
replicates whats done in __BIOVEC_PHYS_MERGEABLE using mfns (bus
addresses). While there also remove the usage of
__BIOVEC_PHYS_MERGEABLE, since that's already checked by the callers
of xen_biovec_phys_mergeable.

CC: stable@vger.kernel.org
Reported-by: "Jan H. Schönherr" <jschoenh@amazon.de>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2017-08-15 10:32:49 -04:00
arch KVM fixes for v4.13-rc2 2017-07-21 13:58:10 -07:00
block blk-mq: map queues to all present CPUs 2017-07-24 10:01:31 -06:00
certs
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-07-14 22:49:50 -07:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-07-20 16:33:39 -07:00
drivers xen: fix bio vec merging 2017-08-15 10:32:49 -04:00
firmware
fs NFS client bugfixes for 4.13 2017-07-21 16:26:01 -07:00
include NFS client bugfixes for 4.13 2017-07-21 16:26:01 -07:00
init
ipc
kernel Three minor updates 2017-07-21 13:59:51 -07:00
lib Add wait_for_random_bytes() and get_random_*_wait() functions so that 2017-07-15 12:44:02 -07:00
mm Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 12:00:42 -07:00
net NFS client bugfixes for 4.13 2017-07-21 16:26:01 -07:00
samples
scripts
security Now that IPC and other changes have landed, enable manual markings for 2017-07-19 08:55:18 -07:00
sound
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-07-21 11:12:48 -07:00
usr
virt Second batch of KVM updates for v4.13 2017-07-15 10:18:16 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: fix alphabetical ordering 2017-07-21 18:59:11 -07:00
Makefile Linux v4.13-rc1 2017-07-15 15:22:10 -07:00
README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.