leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
mainlining shenanigans
1,073,302 Commits 2 Branches 0 Tags 5.1 GiB
C 97.7%
Assembly 1.1%
Shell 0.4%
Makefile 0.3%
Python 0.2%
Other 0.1%
ddbd89deb7
Go to file
Halil Pasic ddbd89deb7 swiotlb: fix info leak with DMA_FROM_DEVICE 
The problem I'm addressing was discovered by the LTP test covering
cve-2018-1000204.

A short description of what happens follows:
1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO
   interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV
   and a corresponding dxferp. The peculiar thing about this is that TUR
   is not reading from the device.
2) In sg_start_req() the invocation of blk_rq_map_user() effectively
   bounces the user-space buffer. As if the device was to transfer into
   it. Since commit a45b599ad8 ("scsi: sg: allocate with __GFP_ZERO in
   sg_build_indirect()") we make sure this first bounce buffer is
   allocated with GFP_ZERO.
3) For the rest of the story we keep ignoring that we have a TUR, so the
   device won't touch the buffer we prepare as if the we had a
   DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device
   and the  buffer allocated by SG is mapped by the function
   virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here
   scatter-gather and not scsi generics). This mapping involves bouncing
   via the swiotlb (we need swiotlb to do virtio in protected guest like
   s390 Secure Execution, or AMD SEV).
4) When the SCSI TUR is done, we first copy back the content of the second
   (that is swiotlb) bounce buffer (which most likely contains some
   previous IO data), to the first bounce buffer, which contains all
   zeros.  Then we copy back the content of the first bounce buffer to
   the user-space buffer.
5) The test case detects that the buffer, which it zero-initialized,
  ain't all zeros and fails.

One can argue that this is an swiotlb problem, because without swiotlb
we leak all zeros, and the swiotlb should be transparent in a sense that
it does not affect the outcome (if all other participants are well
behaved).

Copying the content of the original buffer into the swiotlb buffer is
the only way I can think of to make swiotlb transparent in such
scenarios. So let's do just that if in doubt, but allow the driver
to tell us that the whole mapped buffer is going to be overwritten,
in which case we can preserve the old behavior and avoid the performance
impact of the extra bounce.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2022-02-14 10:22:28 +01:00
arch - Fix a case where objtool would mistakenly warn about instructions being unreachable 2022-02-13 09:43:34 -08:00
block block: bio-integrity: Advance seed correctly for larger interval sizes 2022-02-03 21:09:24 -07:00
certs certs: Fix build error when CONFIG_MODULE_SIG_KEY is empty 2022-01-23 00:08:44 +09:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2022-02-09 09:53:56 -08:00
Documentation swiotlb: fix info leak with DMA_FROM_DEVICE 2022-02-14 10:22:28 +01:00
drivers Interrupt chip driver fixes: 2022-02-13 10:06:40 -08:00
fs 3 small smb3 reconnect fixes and an error log clarification 2022-02-13 09:16:45 -08:00
include swiotlb: fix info leak with DMA_FROM_DEVICE 2022-02-14 10:22:28 +01:00
init lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() 2022-01-22 08:33:37 +02:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-04 09:25:05 -08:00
kernel swiotlb: fix info leak with DMA_FROM_DEVICE 2022-02-14 10:22:28 +01:00
lib lib/crypto: blake2s: avoid indirect calls to compression function for Clang CFI 2022-02-04 19:22:32 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm kfence: make test case compatible with run time set sample interval 2022-02-11 17:55:00 -08:00
net Networking fixes for 5.17-rc4, including fixes from netfilter and can. 2022-02-10 16:01:22 -08:00
samples samples/seccomp: Adjust sample to also provide kill option 2022-02-10 19:09:12 -08:00
scripts kconfig: fix failing to generate auto.conf 2022-02-12 23:24:19 +09:00
security integrity-v5-17-fix 2022-02-07 09:55:14 -08:00
sound ASoC: Fixes for v5.17 2022-02-01 16:52:54 +01:00
tools Tracing fixes: 2022-02-11 10:22:48 -08:00
usr kbuild: remove include/linux/cyclades.h from header file check 2022-01-27 08:51:08 +01:00
virt Two larger x86 series: 2022-01-28 19:00:26 +02:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update Christian Brauner's email address 2022-02-01 11:21:31 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Removing Ohad from remoteproc/rpmsg maintenance 2021-12-08 10:09:40 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS s390 updates for 5.17-rc4 2022-02-12 09:12:44 -08:00
Makefile Linux 5.17-rc4 2022-02-13 12:13:30 -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.