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Dave Martin abf73988a7 arm64: signal: Verify extra data is user-readable in sys_rt_sigreturn
Currently sys_rt_sigreturn() verifies that the base sigframe is
readable, but no similar check is performed on the extra data to
which an extra_context record points.

This matters because the extra data will be read with the
unprotected user accessors.  However, this is not a problem at
present because the extra data base address is required to be
exactly at the end of the base sigframe.  So, there would need to
be a non-user-readable kernel address within about 59K
(SIGFRAME_MAXSZ - sizeof(struct rt_sigframe)) of some address for
which access_ok(VERIFY_READ) returns true, in order for sigreturn
to be able to read kernel memory that should be inaccessible to the
user task.  This is currently impossible due to the untranslatable
address hole between the TTBR0 and TTBR1 address ranges.

Disappearance of the hole between the TTBR0 and TTBR1 mapping
ranges would require the VA size for TTBR0 and TTBR1 to grow to at
least 55 bits, and either the disabling of tagged pointers for
userspace or enabling of tagged pointers for kernel space; none of
which is currently envisaged.

Even so, it is wrong to use the unprotected user accessors without
an accompanying access_ok() check.

To avoid the potential for future surprises, this patch does an
explicit access_ok() check on the extra data space when parsing an
extra_context record.

Fixes: 33f082614c ("arm64: signal: Allow expansion of the signal frame")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2017-11-03 15:24:11 +00:00
arch arm64: signal: Verify extra data is user-readable in sys_rt_sigreturn 2017-11-03 15:24:11 +00:00
block
certs
crypto
Documentation Merge branch 'for-next/perf' into aarch64/for-next/core 2017-10-24 16:06:56 +01:00
drivers arm-ccn: perf: Prevent module unload while PMU is in use 2017-11-03 15:24:06 +00:00
firmware
fs regset: Add support for dynamically sized regsets 2017-11-03 15:24:11 +00:00
include regset: Add support for dynamically sized regsets 2017-11-03 15:24:11 +00:00
init
ipc
kernel perf/core: Export AUX buffer helpers to modules 2017-10-18 12:53:30 +01:00
lib
mm
net
samples
scripts
security
sound
tools
usr
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MAINTAINERS arm64: MAINTAINERS: hisi: Add HiSilicon SoC PMU support 2017-10-19 17:06:35 +01:00
Makefile Linux 4.14-rc3 2017-10-01 14:54:54 -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.