Commit 8eabf42a authored by Baoquan He's avatar Baoquan He Committed by Ingo Molnar

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: default avatarDave Young <dyoung@redhat.com>
Signed-off-by: default avatarBaoquan He <bhe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 8391c73c ("x86/KASLR: Randomize virtual address separately")
Link: http://lkml.kernel.org/r/1498567146-11990-3-git-send-email-bhe@redhat.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent b892cb87
...@@ -564,9 +564,6 @@ void choose_random_location(unsigned long input, ...@@ -564,9 +564,6 @@ void choose_random_location(unsigned long input,
{ {
unsigned long random_addr, min_addr; unsigned long random_addr, min_addr;
/* By default, keep output position unchanged. */
*virt_addr = *output;
if (cmdline_find_option_bool("nokaslr")) { if (cmdline_find_option_bool("nokaslr")) {
warn("KASLR disabled: 'nokaslr' on cmdline."); warn("KASLR disabled: 'nokaslr' on cmdline.");
return; return;
......
...@@ -338,7 +338,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, ...@@ -338,7 +338,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
unsigned long output_len) unsigned long output_len)
{ {
const unsigned long kernel_total_size = VO__end - VO__text; 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. */ /* Retain x86 boot parameters pointer passed from startup_32/64. */
boot_params = rmode; boot_params = rmode;
...@@ -399,7 +399,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, ...@@ -399,7 +399,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
#ifndef CONFIG_RELOCATABLE #ifndef CONFIG_RELOCATABLE
if ((unsigned long)output != LOAD_PHYSICAL_ADDR) if ((unsigned long)output != LOAD_PHYSICAL_ADDR)
error("Destination address does not match 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"); error("Destination virtual address changed when not relocatable");
#endif #endif
......
...@@ -81,8 +81,6 @@ static inline void choose_random_location(unsigned long input, ...@@ -81,8 +81,6 @@ static inline void choose_random_location(unsigned long input,
unsigned long output_size, unsigned long output_size,
unsigned long *virt_addr) unsigned long *virt_addr)
{ {
/* No change from existing output location. */
*virt_addr = *output;
} }
#endif #endif
......
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