From cc6b8fbcc65652d09aef71d0ca232a5c7791a0c7 Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Tue, 27 Jun 2017 20:39:06 +0800 Subject: [PATCH] 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 Signed-off-by: Baoquan He Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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 Signed-off-by: Greg Kroah-Hartman --- 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 8b7c9e75edcbf..8fad8a64d6708 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 b3c5a5f030ced..c945acd8fa334 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; @@ -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 1c8355eadbd19..766a5211f8276 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 -- 2.47.2