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From 7ca60898ccb2e1dc5e47dca5d53eb42922a0a0bc Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Thu, 26 Jul 2018 16:24:47 +0200
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Subject: [PATCH 5/8] multiboot: Reject kernels exceeding the address space
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180726162448.22072-6-kwolf@redhat.com>
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Patchwork-id: 81514
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O-Subject: [RHEL-7.6/7.5.z qemu-kvm PATCH 5/6] multiboot: Reject kernels exceeding the address space
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Bugzilla: 1549822
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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The code path where mh_load_end_addr is non-zero in the Multiboot
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header checks that mh_load_end_addr >= mh_load_addr and so
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mb_load_size is checked. However, mb_load_size is not checked when
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calculated from the file size, when mh_load_end_addr is 0.
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If the kernel binary size is larger than can fit in the address space
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after load_addr, we ended up with a kernel_size that is smaller than
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load_size, which means that we read the file into a too small buffer.
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Add a check to reject kernel files with such Multiboot headers.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
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(cherry picked from commit b17a9054a0652a1481be48a6729e972abf02412f)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/i386/multiboot.c | 4 ++++
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1 file changed, 4 insertions(+)
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diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
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index 56889e8..6f489a5 100644
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--- a/hw/i386/multiboot.c
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+++ b/hw/i386/multiboot.c
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@@ -226,6 +226,10 @@ int load_multiboot(FWCfgState *fw_cfg,
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}
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mb_load_size = kernel_file_size - mb_kernel_text_offset;
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}
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+ if (mb_load_size > UINT32_MAX - mh_load_addr) {
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+ error_report("kernel does not fit in address space");
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+ exit(1);
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+ }
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if (mh_bss_end_addr) {
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if (mh_bss_end_addr < (mh_load_addr + mb_load_size)) {
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error_report("invalid bss_end_addr address");
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--
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1.8.3.1
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