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

commit 8eabf42ae5237e6b699aeac687b5b629e3537c8d upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index a66854d..6de58f1 100644 (file)
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -430,9 +430,6 @@ 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 b3c5a5f..c945acd 100644 (file)
--- 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;
@@ -397,7 +397,7 @@ 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 (file)
--- 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