From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56217) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dpHz3-0007Mi-FL for qemu-devel@nongnu.org; Tue, 05 Sep 2017 13:50:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dpHyy-00074m-L2 for qemu-devel@nongnu.org; Tue, 05 Sep 2017 13:49:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60624) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dpHyy-00074L-Ez for qemu-devel@nongnu.org; Tue, 05 Sep 2017 13:49:52 -0400 From: P J P Date: Tue, 5 Sep 2017 23:19:42 +0530 Message-Id: <20170905174942.3094-1-ppandit@redhat.com> Subject: [Qemu-devel] [PATCH] multiboot: validate multiboot header address values List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Qemu Developers Cc: Paolo Bonzini , Eduardo Habkost , Thomas Garnier , Prasad J Pandit From: Prasad J Pandit 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. Reported-by: Thomas Garnier Signed-off-by: Prasad J Pandit --- hw/i386/multiboot.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c index 6001f4caa2..c7b70c91d5 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; } -- 2.13.5