Currently KASLR only supports relocation in a small physical range (from
16M to 1G), due to using the initial kernel page table identity mapping.
To support ranges above this, we need to have an identity mapping for the
desired memory range before we can decompress (and later run) the kernel.
32-bit kernels already have the needed identity mapping. This patch adds
identity mappings for the needed memory ranges on 64-bit kernels. This
happens in two possible boot paths:
If loaded via startup_32(), we need to set up the needed identity map.
If loaded from a 64-bit bootloader, the bootloader will have already
set up an identity mapping, and we'll start via the compressed kernel's
startup_64(). In this case, the bootloader's page tables need to be
avoided while selecting the new uncompressed kernel location. If not,
the decompressor could overwrite them during decompression.
To accomplish this, we could walk the pagetable and find every page
that is used, and add them to mem_avoid, but this needs extra code and
will require increasing the size of the mem_avoid array.
Instead, we can create a new set of page tables for our own identity
mapping instead. The pages for the new page table will come from the
_pagetable section of the compressed kernel, which means they are
already contained by in mem_avoid array. To do this, we reuse the code
from the uncompressed kernel's identity mapping routines.
The _pgtable will be shared by both the 32-bit and 64-bit paths to reduce
init_size, as now the compressed kernel's _rodata to _end will contribute
to init_size.
To handle the possible mappings, we need to increase the existing page
table buffer size:
When booting via startup_64(), we need to cover the old VO, params,
cmdline and uncompressed kernel. In an extreme case we could have them
all beyond the 512G boundary, which needs (2+2)*4 pages with 2M mappings.
And we'll need 2 for first 2M for VGA RAM. One more is needed for level4.
This gets us to 19 pages total.
When booting via startup_32(), KASLR could move the uncompressed kernel
above 4G, so we need to create extra identity mappings, which should only
need (2+2) pages at most when it is beyond the 512G boundary. So 19
pages is sufficient for this case as well.
The resulting BOOT_*PGT_SIZE defines use the "_SIZE" suffix on their
names to maintain logical consistency with the existing BOOT_HEAP_SIZE
and BOOT_STACK_SIZE defines.
This patch is based on earlier patches from Yinghai Lu and Baoquan He.
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: lasse.collin@tukaani.org
Link: http://lkml.kernel.org/r/1462572095-11754-4-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently extract_kernel() defines the input and output buffer pointers
as "unsigned char *" since that's effectively what they are. It passes
these to the decompressor routine and to the ELF parser, which both
logically deal with buffer pointers too. There is some casting ("unsigned
long") done to validate the numerical value of the pointers, but it is
relatively limited.
However, choose_random_location() operates almost exclusively on the
numerical representation of these pointers, so it ended up carrying
a lot of "unsigned long" casts. With the future physical/virtual split
these casts were going to multiply, so this attempts to solve the
problem by doing all the casting in choose_random_location()'s entry
and return instead of through-out the code. Adjusts argument names to
be more meaningful, and changes one us of "choice" to "output" to make
the future physical/virtual split more clear (i.e. "choice" should be
strictly a function return value and not used as an intermediate).
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: lasse.collin@tukaani.org
Link: http://lkml.kernel.org/r/1462486436-3707-2-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently, the "run_size" variable holds the total kernel size
(size of code plus brk and bss) and is calculated via the shell script
arch/x86/tools/calc_run_size.sh. It gets the file offset and mem size
of the .bss and .brk sections from the vmlinux, and adds them as follows:
run_size = $(( $offsetA + $sizeA + $sizeB ))
However, this is not correct (it is too large). To illustrate, here's
a walk-through of the script's calculation, compared to the correct way
to find it.
First, offsetA is found as the starting address of the first .bss or
.brk section seen in the ELF file. The sizeA and sizeB values are the
respective section sizes.
[bhe@x1 linux]$ objdump -h vmlinux
vmlinux: file format elf64-x86-64
Sections:
Idx Name Size VMA LMA File off Algn
27 .bss 00170000 ffffffff81ec8000 0000000001ec8000 012c8000 2**12
ALLOC
28 .brk 00027000 ffffffff82038000 0000000002038000 012c8000 2**0
ALLOC
Here, offsetA is 0x012c8000, with sizeA at 0x00170000 and sizeB at
0x00027000. The resulting run_size is 0x145f000:
0x012c8000 + 0x00170000 + 0x00027000 = 0x145f000
However, if we instead examine the ELF LOAD program headers, we see a
different picture.
[bhe@x1 linux]$ readelf -l vmlinux
Elf file type is EXEC (Executable file)
Entry point 0x1000000
There are 5 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000200000 0xffffffff81000000 0x0000000001000000
0x0000000000b5e000 0x0000000000b5e000 R E 200000
LOAD 0x0000000000e00000 0xffffffff81c00000 0x0000000001c00000
0x0000000000145000 0x0000000000145000 RW 200000
LOAD 0x0000000001000000 0x0000000000000000 0x0000000001d45000
0x0000000000018158 0x0000000000018158 RW 200000
LOAD 0x000000000115e000 0xffffffff81d5e000 0x0000000001d5e000
0x000000000016a000 0x0000000000301000 RWE 200000
NOTE 0x000000000099bcac 0xffffffff8179bcac 0x000000000179bcac
0x00000000000001bc 0x00000000000001bc 4
Section to Segment mapping:
Segment Sections...
00 .text .notes __ex_table .rodata __bug_table .pci_fixup .tracedata
__ksymtab __ksymtab_gpl __ksymtab_strings __init_rodata __param
__modver
01 .data .vvar
02 .data..percpu
03 .init.text .init.data .x86_cpu_dev.init .parainstructions
.altinstructions .altinstr_replacement .iommu_table .apicdrivers
.exit.text .smp_locks .bss .brk
04 .notes
As mentioned, run_size needs to be the size of the running kernel
including .bss and .brk. We can see from the Section/Segment mapping
above that .bss and .brk are included in segment 03 (which corresponds
to the final LOAD program header). To find the run_size, we calculate
the end of the LOAD segment from its PhysAddr start (0x0000000001d5e000)
and its MemSiz (0x0000000000301000), minus the physical load address of
the kernel (the first LOAD segment's PhysAddr: 0x0000000001000000). The
resulting run_size is 0x105f000:
0x0000000001d5e000 + 0x0000000000301000 - 0x0000000001000000 = 0x105f000
So, from this we can see that the existing run_size calculation is
0x400000 too high. And, as it turns out, the correct run_size is
actually equal to VO_end - VO_text, which is certainly easier to calculate.
_end: 0xffffffff8205f000
_text:0xffffffff81000000
0xffffffff8205f000 - 0xffffffff81000000 = 0x105f000
As a result, run_size is a simple constant, so we don't need to pass it
around; we already have voffset.h for such things. We can share voffset.h
between misc.c and header.S instead of getting run_size in other ways.
This patch moves voffset.h creation code to boot/compressed/Makefile,
and switches misc.c to use the VO_end - VO_text calculation for run_size.
Dependence before:
boot/header.S ==> boot/voffset.h ==> vmlinux
boot/header.S ==> compressed/vmlinux ==> compressed/misc.c
Dependence after:
boot/header.S ==> compressed/vmlinux ==> compressed/misc.c ==> boot/voffset.h ==> vmlinux
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Baoquan He <bhe@redhat.com>
[ Rewrote the changelog. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Junjie Mao <eternal.n08@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: lasse.collin@tukaani.org
Fixes: e6023367d7 ("x86, kaslr: Prevent .bss from overlaping initrd")
Link: http://lkml.kernel.org/r/1461888548-32439-5-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently z_extract_offset is calculated in boot/compressed/mkpiggy.c.
This doesn't work well because mkpiggy.c doesn't know the details of the
decompressor in use. As a result, it can only make an estimation, which
has risks:
- output + output_len (VO) could be much bigger than input + input_len
(ZO). In this case, the decompressed kernel plus relocs could overwrite
the decompression code while it is running.
- The head code of ZO could be bigger than z_extract_offset. In this case
an overwrite could happen when the head code is running to move ZO to
the end of buffer. Though currently the size of the head code is very
small it's still a potential risk. Since there is no rule to limit the
size of the head code of ZO, it runs the risk of suddenly becoming a
(hard to find) bug.
Instead, this moves the z_extract_offset calculation into header.S, and
makes adjustments to be sure that the above two cases can never happen,
and further corrects the comments describing the calculations.
Since we have (in the previous patch) made ZO always be located against
the end of decompression buffer, z_extract_offset is only used here to
calculate an appropriate buffer size (INIT_SIZE), and is not longer used
elsewhere. As such, it can be removed from voffset.h.
Additionally clean up #if/#else #define to improve readability.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Baoquan He <bhe@redhat.com>
[ Rewrote the changelog and comments. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: lasse.collin@tukaani.org
Link: http://lkml.kernel.org/r/1461888548-32439-4-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This change makes later calculations about where the kernel is located
easier to reason about. To better understand this change, we must first
clarify what 'VO' and 'ZO' are. These values were introduced in commits
by hpa:
77d1a49995 ("x86, boot: make symbols from the main vmlinux available")
37ba7ab5e3 ("x86, boot: make kernel_alignment adjustable; new bzImage fields")
Specifically:
All names prefixed with 'VO_':
- relate to the uncompressed kernel image
- the size of the VO image is: VO__end-VO__text ("VO_INIT_SIZE" define)
All names prefixed with 'ZO_':
- relate to the bootable compressed kernel image (boot/compressed/vmlinux),
which is composed of the following memory areas:
- head text
- compressed kernel (VO image and relocs table)
- decompressor code
- the size of the ZO image is: ZO__end - ZO_startup_32 ("ZO_INIT_SIZE" define, though see below)
The 'INIT_SIZE' value is used to find the larger of the two image sizes:
#define ZO_INIT_SIZE (ZO__end - ZO_startup_32 + ZO_z_extract_offset)
#define VO_INIT_SIZE (VO__end - VO__text)
#if ZO_INIT_SIZE > VO_INIT_SIZE
# define INIT_SIZE ZO_INIT_SIZE
#else
# define INIT_SIZE VO_INIT_SIZE
#endif
The current code uses extract_offset to decide where to position the
copied ZO (i.e. ZO starts at extract_offset). (This is why ZO_INIT_SIZE
currently includes the extract_offset.)
Why does z_extract_offset exist? It's needed because we are trying to minimize
the amount of RAM used for the whole act of creating an uncompressed, executable,
properly relocation-linked kernel image in system memory. We do this so that
kernels can be booted on even very small systems.
To achieve the goal of minimal memory consumption we have implemented an in-place
decompression strategy: instead of cleanly separating the VO and ZO images and
also allocating some memory for the decompression code's runtime needs, we instead
create this elaborate layout of memory buffers where the output (decompressed)
stream, as it progresses, overlaps with and destroys the input (compressed)
stream. This can only be done safely if the ZO image is placed to the end of the
VO range, plus a certain amount of safety distance to make sure that when the last
bytes of the VO range are decompressed, the compressed stream pointer is safely
beyond the end of the VO range.
z_extract_offset is calculated in arch/x86/boot/compressed/mkpiggy.c during
the build process, at a point when we know the exact compressed and
uncompressed size of the kernel images and can calculate this safe minimum
offset value. (Note that the mkpiggy.c calculation is not perfect, because
we don't know the decompressor used at that stage, so the z_extract_offset
calculation is necessarily imprecise and is mostly based on gzip internals -
we'll improve that in the next patch.)
When INIT_SIZE is bigger than VO_INIT_SIZE (uncommon but possible),
the copied ZO occupies the memory from extract_offset to the end of
decompression buffer. It overlaps with the soon-to-be-uncompressed kernel
like this:
|-----compressed kernel image------|
V V
0 extract_offset +INIT_SIZE
|-----------|---------------|-------------------------|--------|
| | | |
VO__text startup_32 of ZO VO__end ZO__end
^ ^
|-------uncompressed kernel image---------|
When INIT_SIZE is equal to VO_INIT_SIZE (likely) there's still space
left from end of ZO to the end of decompressing buffer, like below.
|-compressed kernel image-|
V V
0 extract_offset +INIT_SIZE
|-----------|---------------|-------------------------|--------|
| | | |
VO__text startup_32 of ZO ZO__end VO__end
^ ^
|------------uncompressed kernel image-------------|
To simplify calculations and avoid special cases, it is cleaner to
always place the compressed kernel image in memory so that ZO__end
is at the end of the decompression buffer, instead of placing t at
the start of extract_offset as is currently done.
This patch adds BP_init_size (which is the INIT_SIZE as passed in from
the boot_params) into asm-offsets.c to make it visible to the assembly
code.
Then when moving the ZO, it calculates the starting position of
the copied ZO (via BP_init_size and the ZO run size) so that the VO__end
will be at the end of the decompression buffer. To make the position
calculation safe, the end of ZO is page aligned (and a comment is added
to the existing VO alignment for good measure).
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
[ Rewrote changelog and comments. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: lasse.collin@tukaani.org
Link: http://lkml.kernel.org/r/1461888548-32439-3-git-send-email-keescook@chromium.org
[ Rewrote the changelog some more. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The comment that describes the analysis for the size of the decompressor
code only took gzip into account (there are currently 6 other decompressors
that could be used). The actual z_extract_offset calculation in code was
already handling the correct maximum size, but this documentation hadn't
been updated. This updates the documentation, fixes several typos, moves
the comment to header.S, updates references, and adds a note at the end
of the decompressor include list to remind us about updating the comment
in the future.
(Instead of moving the comment to mkpiggy.c, where the calculation
is currently happening, it is being moved to header.S because
the calculations in mkpiggy.c will be removed in favor of header.S
calculations in a following patch, and it seemed like overkill to move
the giant comment twice, especially when there's already reference to
z_extract_offset in header.S.)
Signed-off-by: Baoquan He <bhe@redhat.com>
[ Rewrote changelog, cleaned up comment style, moved comments around. ]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1461185746-8017-2-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull device mapper fix from Mike Snitzer:
"Fix for earlier 4.6-rc4 stable@ commit that introduced improper use of
write lock in cmd_read_lock() -- due to cut-n-paste gone awry (and
sparse didn't catch it)"
* tag 'dm-4.6-fix-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
dm cache metadata: fix cmd_read_lock() acquiring write lock
Commit 9567366fef ("dm cache metadata: fix READ_LOCK macros and
cleanup WRITE_LOCK macros") uses down_write() instead of down_read() in
cmd_read_lock(), yet up_read() is used to release the lock in
READ_UNLOCK(). Fix it.
Fixes: 9567366fef ("dm cache metadata: fix READ_LOCK macros and cleanup WRITE_LOCK macros")
Cc: stable@vger.kernel.org
Signed-off-by: Ahmed Samy <f.fallen45@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Pull char/misc fixes from Greg KH:
"Here are some small char/misc driver fixes for 4.6-rc4. Full details
are in the shortlog, nothing major here.
These have all been in linux-next for a while with no reported issues"
* tag 'char-misc-4.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
lkdtm: do not leak free page on kmalloc failure
lkdtm: fix memory leak of base
lkdtm: fix memory leak of val
extcon: palmas: Drop stray IRQF_EARLY_RESUME flag
Pull misc fixes from Greg KH:
"Here are three small fixes for 4.6-rc4.
Two fix up some lz4 issues with big endian systems, and the remaining
one resolves a minor debugfs issue that was reported.
All have been in linux-next with no reported issues"
* tag 'driver-core-4.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
lib: lz4: cleanup unaligned access efficiency detection
lib: lz4: fixed zram with lz4 on big endian machines
debugfs: Make automount point inodes permanently empty
Pull USB driver fixes from Greg KH:
"Here are some small USB fixes for 4.6-rc4.
Mostly xhci fixes for reported issues, a UAS bug that has hit a number
of people, including stable tree users, and a few other minor things.
All have been in linux-next for a while with no reported issues"
* tag 'usb-4.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
usb: hcd: out of bounds access in for_each_companion
USB: uas: Add a new NO_REPORT_LUNS quirk
USB: uas: Limit qdepth at the scsi-host level
doc: usb: Fix typo in gadget_multi documentation
usb: host: xhci-plat: Make enum xhci_plat_type start at a non zero value
xhci: fix 10 second timeout on removal of PCI hotpluggable xhci controllers
usb: xhci: fix wild pointers in xhci_mem_cleanup
usb: host: xhci-plat: fix cannot work if R-Car Gen2/3 run on above 4GB phys
usb: host: xhci: add a new quirk XHCI_NO_64BIT_SUPPORT
xhci: resume USB 3 roothub first
usb: xhci: applying XHCI_PME_STUCK_QUIRK to Intel BXT B0 host
cdc-acm: fix crash if flushed with nothing buffered
Pull dmaengine fixes from Vinod Koul:
"This time we have some odd fixes in hsu, edma, omap and xilinx.
Usual fixes and nothing special"
* tag 'dmaengine-fix-4.6-rc4' of git://git.infradead.org/users/vkoul/slave-dma:
dmaengine: dw: fix master selection
dmaengine: edma: special case slot limit workaround
dmaengine: edma: Remove dynamic TPTC power management feature
dmaengine: vdma: don't crash when bad channel is requested
dmaengine: omap-dma: Do not suppress interrupts for memcpy
dmaengine: omap-dma: Fix polled channel completion detection and handling
dmaengine: hsu: correct use of channel status register
dmaengine: hsu: correct residue calculation of active descriptor
dmaengine: hsu: set HSU_CH_MTSR to memory width
