From abead8461f6c8c50cdc8dedc43e4821a7e1d5e33 Mon Sep 17 00:00:00 2001 From: Bandan Das Date: Thu, 26 Oct 2017 10:03:48 +0200 Subject: [PATCH 1/2] multiboot: validate multiboot header address values RH-Author: Bandan Das Message-id: Patchwork-id: 77443 O-Subject: [RHEL-7.5 qemu-kvm PATCH] multiboot: validate multiboot header address values Bugzilla: 1501121 RH-Acked-by: Thomas Huth RH-Acked-by: Laurent Vivier RH-Acked-by: Peter Xu 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 09211e0..7eec230 100644 --- a/hw/i386/multiboot.c +++ b/hw/i386/multiboot.c @@ -200,15 +200,34 @@ 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