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