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From abead8461f6c8c50cdc8dedc43e4821a7e1d5e33 Mon Sep 17 00:00:00 2001
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From: Bandan Das <bsd@redhat.com>
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Date: Thu, 26 Oct 2017 10:03:48 +0200
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Subject: [PATCH 1/2] multiboot: validate multiboot header address values
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RH-Author: Bandan Das <bsd@redhat.com>
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Message-id: <jpgefpqw7i3.fsf@linux.bootlegged.copy>
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Patchwork-id: 77443
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O-Subject: [RHEL-7.5 qemu-kvm PATCH] multiboot: validate multiboot header address values
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Bugzilla: 1501121
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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While loading kernel via multiboot-v1 image, (flags & 0x00010000)
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indicates that multiboot header contains valid addresses to load
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the kernel image. These addresses are used to compute kernel
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size and kernel text offset in the OS image. Validate these
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address values to avoid an OOB access issue.
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This is CVE-2017-14167.
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Reported-by: Thomas Garnier <thgarnie@google.com>
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Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
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Message-Id: <20170907063256.7418-1-ppandit@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit ed4f86e8b6eff8e600c69adee68c7cd34dd2cccb)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/i386/multiboot.c | 19 +++++++++++++++++++
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1 file changed, 19 insertions(+)
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diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
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index 09211e0..7eec230 100644
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--- a/hw/i386/multiboot.c
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+++ b/hw/i386/multiboot.c
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@@ -200,15 +200,34 @@ int load_multiboot(FWCfgState *fw_cfg,
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uint32_t mh_header_addr = ldl_p(header+i+12);
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uint32_t mh_load_end_addr = ldl_p(header+i+20);
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uint32_t mh_bss_end_addr = ldl_p(header+i+24);
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+
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mh_load_addr = ldl_p(header+i+16);
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+ if (mh_header_addr < mh_load_addr) {
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+ fprintf(stderr, "invalid mh_load_addr address\n");
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+ exit(1);
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+ }
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+
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uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
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uint32_t mb_load_size = 0;
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mh_entry_addr = ldl_p(header+i+28);
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if (mh_load_end_addr) {
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+ if (mh_bss_end_addr < mh_load_addr) {
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+ fprintf(stderr, "invalid mh_bss_end_addr address\n");
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+ exit(1);
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+ }
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mb_kernel_size = mh_bss_end_addr - mh_load_addr;
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+
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+ if (mh_load_end_addr < mh_load_addr) {
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+ fprintf(stderr, "invalid mh_load_end_addr address\n");
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+ exit(1);
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+ }
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mb_load_size = mh_load_end_addr - mh_load_addr;
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} else {
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+ if (kernel_file_size < mb_kernel_text_offset) {
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+ fprintf(stderr, "invalid kernel_file_size\n");
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+ exit(1);
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+ }
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mb_kernel_size = kernel_file_size - mb_kernel_text_offset;
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mb_load_size = mb_kernel_size;
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}
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--
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1.8.3.1
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