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Baoquan He ec3937107a x86/mm/KASLR: Fix the size of the direct mapping section 
kernel_randomize_memory() uses __PHYSICAL_MASK_SHIFT to calculate
the maximum amount of system RAM supported. The size of the direct
mapping section is obtained from the smaller one of the below two
values:

  (actual system RAM size + padding size) vs (max system RAM size supported)

This calculation is wrong since commit

  b83ce5ee91 ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52").

In it, __PHYSICAL_MASK_SHIFT was changed to be 52, regardless of whether
the kernel is using 4-level or 5-level page tables. Thus, it will always
use 4 PB as the maximum amount of system RAM, even in 4-level paging
mode where it should actually be 64 TB.

Thus, the size of the direct mapping section will always
be the sum of the actual system RAM size plus the padding size.

Even when the amount of system RAM is 64 TB, the following layout will
still be used. Obviously KALSR will be weakened significantly.

   |____|_______actual RAM_______|_padding_|______the rest_______|
   0            64TB                                            ~120TB

Instead, it should be like this:

   |____|_______actual RAM_______|_________the rest______________|
   0            64TB                                            ~120TB

The size of padding region is controlled by
CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING, which is 10 TB by default.

The above issue only exists when
CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING is set to a non-zero value,
which is the case when CONFIG_MEMORY_HOTPLUG is enabled. Otherwise,
using __PHYSICAL_MASK_SHIFT doesn't affect KASLR.

Fix it by replacing __PHYSICAL_MASK_SHIFT with MAX_PHYSMEM_BITS.

 [ bp: Massage commit message. ]

Fixes: b83ce5ee91 ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52")
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: frank.ramsay@hpe.com
Cc: herbert@gondor.apana.org.au
Cc: kirill@shutemov.name
Cc: mike.travis@hpe.com
Cc: thgarnie@google.com
Cc: x86-ml <x86@kernel.org>
Cc: yamada.masahiro@socionext.com
Link: https://lkml.kernel.org/r/20190417083536.GE7065@MiWiFi-R3L-srv
2019-04-18 10:42:58 +02:00
arch x86/mm/KASLR: Fix the size of the direct mapping section 2019-04-18 10:42:58 +02:00
block io_uring-20190323 2019-03-23 10:25:12 -07:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto lib/lzo: separate lzo-rle from lzo 2019-03-07 18:32:03 -08:00
Documentation irqchip updates for 5.1, take #2 2019-03-21 12:30:54 +01:00
drivers Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-24 11:09:47 -07:00
fs Miscellaneous ext4 bug fixes for 5.1. 2019-03-24 13:41:37 -07:00
include x86/reboot, efi: Use EFI reboot for Acer TravelMate X514-51T 2019-04-16 10:01:24 +02:00
init init/main: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
ipc Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
kernel Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-24 11:42:10 -07:00
lib Kbuild updates for v5.1 (2nd) 2019-03-17 13:25:26 -07:00
LICENSES LICENSES: Add GCC runtime library exception text 2019-01-16 14:54:15 -07:00
mm device-dax for 5.1 2019-03-16 13:05:32 -07:00
net libceph: wait for latest osdmap in ceph_monc_blacklist_add() 2019-03-20 16:27:40 +01:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-11 08:54:01 -07:00
scripts kconfig: remove stale lxdialog/.gitignore 2019-03-17 15:47:02 +09:00
security selinux: fix NULL dereference in policydb_destroy() 2019-03-18 12:19:48 -04:00
sound sound fixes for 5.1-rc2 2019-03-22 14:04:38 -07:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-24 11:16:27 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt ARM: some cleanups, direct physical timer assignment, cache sanitization 2019-03-15 15:00:28 -07:00
.clang-format Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 13:43:42 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap .mailmap: Add Mathieu Othacehe 2019-02-21 11:41:19 +00:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS io_uring-20190323 2019-03-23 10:25:12 -07:00
Makefile Linux 5.1-rc2 2019-03-24 14:02:26 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.