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x86/boot/KASLR: Fix kexec crash due to 'virt_addr' calculation bug 

Kernel text KASLR is separated into physical address and virtual
address randomization. And for virtual address randomization, we
only randomiza to get an offset between 16M and KERNEL_IMAGE_SIZE.
So the initial value of 'virt_addr' should be LOAD_PHYSICAL_ADDR,
but not the original kernel loading address 'output'.

The bug will cause kernel boot failure if kernel is loaded at a different
position than the address, 16M, which is decided at compiled time.
Kexec/kdump is such practical case.

To fix it, just assign LOAD_PHYSICAL_ADDR to virt_addr as initial
value.

Tested-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 8391c73 ("x86/KASLR: Randomize virtual address separately")
Link: http://lkml.kernel.org/r/1498567146-11990-3-git-send-email-bhe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Baoquan He 2017-06-27 20:39:06 +08:00 committed by Ingo Molnar
parent b892cb873c
commit 8eabf42ae5
3 changed files with 2 additions and 7 deletions
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3
arch/x86/boot/compressed/kaslr.c
View File

@ -564,9 +564,6 @@ void choose_random_location(unsigned long input,
{
unsigned long random_addr, min_addr;
/* By default, keep output position unchanged. */
*virt_addr = *output;
if (cmdline_find_option_bool("nokaslr")) {
warn("KASLR disabled: 'nokaslr' on cmdline.");
return;

4
arch/x86/boot/compressed/misc.c
View File

@ -338,7 +338,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
unsigned long output_len)
{
const unsigned long kernel_total_size = VO__end - VO__text;
unsigned long virt_addr = (unsigned long)output;
unsigned long virt_addr = LOAD_PHYSICAL_ADDR;
/* Retain x86 boot parameters pointer passed from startup_32/64. */
boot_params = rmode;
@ -399,7 +399,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
#ifndef CONFIG_RELOCATABLE
if ((unsigned long)output != LOAD_PHYSICAL_ADDR)
error("Destination address does not match LOAD_PHYSICAL_ADDR");
if ((unsigned long)output != virt_addr)
if (virt_addr != LOAD_PHYSICAL_ADDR)
error("Destination virtual address changed when not relocatable");
#endif

2
arch/x86/boot/compressed/misc.h
View File

@ -81,8 +81,6 @@ static inline void choose_random_location(unsigned long input,
unsigned long output_size,
unsigned long *virt_addr)
{
/* No change from existing output location. */
*virt_addr = *output;
}
#endif