From 6eb6532f3da50fab83585197c446b86503900e15 Mon Sep 17 00:00:00 2001 From: Bandan Das Date: Thu, 26 Oct 2017 09:55:58 +0200 Subject: [PATCH 2/2] multiboot: validate multiboot header address values RH-Author: Bandan Das Message-id: Patchwork-id: 77442 O-Subject: [RHV7.5 qemu-kvm-rhev PATCH] multiboot: validate multiboot header address values Bugzilla: 1501123 RH-Acked-by: Thomas Huth RH-Acked-by: Peter Xu RH-Acked-by: Miroslav Rezanina While loading kernel via multiboot-v1 image, (flags & 0x00010000) indicates that multiboot header contains valid addresses to load the kernel image. These addresses are used to compute kernel size and kernel text offset in the OS image. Validate these address values to avoid an OOB access issue. This is CVE-2017-14167. Reported-by: Thomas Garnier Signed-off-by: Prasad J Pandit Message-Id: <20170907063256.7418-1-ppandit@redhat.com> Signed-off-by: Paolo Bonzini (cherry picked from commit ed4f86e8b6eff8e600c69adee68c7cd34dd2cccb) Signed-off-by: Miroslav Rezanina --- hw/i386/multiboot.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c index f13e231..22688d3 100644 --- a/hw/i386/multiboot.c +++ b/hw/i386/multiboot.c @@ -221,15 +221,34 @@ int load_multiboot(FWCfgState *fw_cfg, uint32_t mh_header_addr = ldl_p(header+i+12); uint32_t mh_load_end_addr = ldl_p(header+i+20); uint32_t mh_bss_end_addr = ldl_p(header+i+24); + mh_load_addr = ldl_p(header+i+16); + if (mh_header_addr < mh_load_addr) { + fprintf(stderr, "invalid mh_load_addr address\n"); + exit(1); + } + uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr); uint32_t mb_load_size = 0; mh_entry_addr = ldl_p(header+i+28); if (mh_load_end_addr) { + if (mh_bss_end_addr < mh_load_addr) { + fprintf(stderr, "invalid mh_bss_end_addr address\n"); + exit(1); + } mb_kernel_size = mh_bss_end_addr - mh_load_addr; + + if (mh_load_end_addr < mh_load_addr) { + fprintf(stderr, "invalid mh_load_end_addr address\n"); + exit(1); + } mb_load_size = mh_load_end_addr - mh_load_addr; } else { + if (kernel_file_size < mb_kernel_text_offset) { + fprintf(stderr, "invalid kernel_file_size\n"); + exit(1); + } mb_kernel_size = kernel_file_size - mb_kernel_text_offset; mb_load_size = mb_kernel_size; } -- 1.8.3.1