From b892cb873ced2af57dc5a018557d128c53ed6ae0 Mon Sep 17 00:00:00 2001 From: Baoquan He Date: Tue, 27 Jun 2017 20:39:05 +0800 Subject: [PATCH] x86/boot/KASLR: Add checking for the offset of kernel virtual address randomization For kernel text KASLR, the virtual address is confined to area of 1G, [0xffffffff80000000, 0xffffffffc0000000). For the implemenataion of virtual address randomization, we only randomize to get an offset between 16M and 1G, then add this offset to the starting address, 0xffffffff80000000. Here 16M is the offset which is decided at linking stage. So the amount of the local variable 'virt_addr' which respresents the offset plus the kernel output size can not exceed KERNEL_IMAGE_SIZE. Add a debug check for the offset. If out of bounds, print error message and hang there. Suggested-by: Ingo Molnar Signed-off-by: Baoquan He Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1498567146-11990-2-git-send-email-bhe@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/boot/compressed/misc.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index b3c5a5f030ce..6008fa9b74d9 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -390,6 +390,8 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, #ifdef CONFIG_X86_64 if (heap > 0x3fffffffffffUL) error("Destination address too large"); + if (virt_addr + max(output_len, kernel_total_size) > KERNEL_IMAGE_SIZE) + error("Destination virtual address is beyond the kernel mapping area"); #else if (heap > ((-__PAGE_OFFSET-(128<<20)-1) & 0x7fffffff)) error("Destination address too large");