[tip:x86/urgent] x86/boot/KASLR: Fix kexec crash due to 'virt_addr' calculation bug
From: tip-bot for Baoquan He
Date: Fri Jun 30 2017 - 09:12:41 EST
Commit-ID: 8eabf42ae5237e6b699aeac687b5b629e3537c8d
Gitweb: http://git.kernel.org/tip/8eabf42ae5237e6b699aeac687b5b629e3537c8d
Author: Baoquan He <bhe@xxxxxxxxxx>
AuthorDate: Tue, 27 Jun 2017 20:39:06 +0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 30 Jun 2017 08:53:14 +0200
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@xxxxxxxxxx>
Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: 8391c73 ("x86/KASLR: Randomize virtual address separately")
Link: http://lkml.kernel.org/r/1498567146-11990-3-git-send-email-bhe@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/boot/compressed/kaslr.c | 3 ---
arch/x86/boot/compressed/misc.c | 4 ++--
arch/x86/boot/compressed/misc.h | 2 --
3 files changed, 2 insertions(+), 7 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 54c24f0..56a7e92 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -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;
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 6008fa9..00241c8 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -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
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 1c8355e..766a521 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -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