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Andrey Konovalov a064cb00d3 kasan: initialize shadow to TAG_INVALID for SW_TAGS
Currently, KASAN_SW_TAGS uses 0xFF as the default tag value for
unallocated memory.  The underlying idea is that since that memory hasn't
been allocated yet, it's only supposed to be dereferenced through a
pointer with the native 0xFF tag.

While this is a good idea in terms on consistency, practically it doesn't
bring any benefit.  Since the 0xFF pointer tag is a match-all tag, it
doesn't matter what tag the accessed memory has.  No accesses through
0xFF-tagged pointers are considered buggy by KASAN.

This patch changes the default tag value for unallocated memory to 0xFE,
which is the tag KASAN uses for inaccessible memory.  This doesn't affect
accesses through 0xFF-tagged pointer to this memory, but this allows KASAN
to detect wild and large out-of-bounds invalid memory accesses through
otherwise-tagged pointers.

This is a prepatory patch for the next one, which changes the tag-based
KASAN modes to not poison the boot memory.

Link: https://lkml.kernel.org/r/c8e93571c18b3528aac5eb33ade213bf133d10ad.1613692950.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-30 11:20:41 -07:00
arch mm/vmalloc: remove unmap_kernel_range 2021-04-30 11:20:40 -07:00
block cgroup: rstat: punt root-level optimization to individual controllers 2021-04-30 11:20:37 -07:00
certs
crypto
Documentation mm/doc: add mm.h and mm_types.h to the mm-api document 2021-04-30 11:20:41 -07:00
drivers mm/vmalloc: remove unmap_kernel_range 2021-04-30 11:20:40 -07:00
fs Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" 2021-04-30 11:20:39 -07:00
include kasan: initialize shadow to TAG_INVALID for SW_TAGS 2021-04-30 11:20:41 -07:00
init mm: HUGE_VMAP arch support cleanup 2021-04-30 11:20:40 -07:00
ipc
kernel kernel/dma: remove unnecessary unmap_kernel_range 2021-04-30 11:20:40 -07:00
lib lib/test_vmalloc.c: add a new 'nr_threads' parameter 2021-04-30 11:20:40 -07:00
LICENSES
mm kasan: fix kasan_byte_accessible() to be consistent with actual checks 2021-04-30 11:20:41 -07:00
net
samples samples/vfio-mdev/mdpy: use remap_vmalloc_range 2021-04-30 11:20:39 -07:00
scripts
security
sound
tools vm/test_vmalloc.sh: adapt for updated driver interface 2021-04-30 11:20:40 -07:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: assign pagewalk.h to MEMORY MANAGEMENT 2021-04-30 11:20:41 -07:00
Makefile
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.