diff options
| author | Junjie Mao <eternal.n08@gmail.com> | 2014-10-31 21:40:38 +0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2014-11-01 22:20:50 +0100 |
| commit | e6023367d779060fddc9a52d1f474085b2b36298 (patch) | |
| tree | ef35781f63032842e6cf8b3e1869d54f312ce17f /arch/x86/boot/compressed/head_32.S | |
| parent | 4750a0d112cbfcc744929f1530ffe3193436766c (diff) | |
x86, kaslr: Prevent .bss from overlaping initrd
When choosing a random address, the current implementation does not take into
account the reversed space for .bss and .brk sections. Thus the relocated kernel
may overlap other components in memory. Here is an example of the overlap from a
x86_64 kernel in qemu (the ranges of physical addresses are presented):
Physical Address
0x0fe00000 --+--------------------+ <-- randomized base
/ | relocated kernel |
vmlinux.bin | (from vmlinux.bin) |
0x1336d000 (an ELF file) +--------------------+--
\ | | \
0x1376d870 --+--------------------+ |
| relocs table | |
0x13c1c2a8 +--------------------+ .bss and .brk
| | |
0x13ce6000 +--------------------+ |
| | /
0x13f77000 | initrd |--
| |
0x13fef374 +--------------------+
The initrd image will then be overwritten by the memset during early
initialization:
[ 1.655204] Unpacking initramfs...
[ 1.662831] Initramfs unpacking failed: junk in compressed archive
This patch prevents the above situation by requiring a larger space when looking
for a random kernel base, so that existing logic can effectively avoids the
overlap.
[kees: switched to perl to avoid hex translation pain in mawk vs gawk]
[kees: calculated overlap without relocs table]
Fixes: 82fa9637a2 ("x86, kaslr: Select random position from e820 maps")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Junjie Mao <eternal.n08@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1414762838-13067-1-git-send-email-eternal.n08@gmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/boot/compressed/head_32.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index cbed1407a5cd..1d7fbbcc196d 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -207,7 +207,8 @@ relocated: * Do the decompression, and jump to the new kernel.. */ /* push arguments for decompress_kernel: */ - pushl $z_output_len /* decompressed length */ + pushl $z_run_size /* size of kernel with .bss and .brk */ + pushl $z_output_len /* decompressed length, end of relocs */ leal z_extract_offset_negative(%ebx), %ebp pushl %ebp /* output address */ pushl $z_input_len /* input_len */ @@ -217,7 +218,7 @@ relocated: pushl %eax /* heap area */ pushl %esi /* real mode pointer */ call decompress_kernel /* returns kernel location in %eax */ - addl $24, %esp + addl $28, %esp /* * Jump to the decompressed kernel. |