From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37454) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eyevc-0006qK-UB for qemu-devel@nongnu.org; Wed, 21 Mar 2018 10:41:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eyeva-0002Cn-QI for qemu-devel@nongnu.org; Wed, 21 Mar 2018 10:41:24 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:34824 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eyeva-0002Ca-ME for qemu-devel@nongnu.org; Wed, 21 Mar 2018 10:41:22 -0400 From: Kevin Wolf Date: Wed, 21 Mar 2018 15:41:03 +0100 Message-Id: <20180321144107.22770-2-kwolf@redhat.com> In-Reply-To: <20180321144107.22770-1-kwolf@redhat.com> References: <20180321144107.22770-1-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 1/5] multiboot: Reject kernels exceeding the address space List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, peter.maydell@linaro.org 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 --- hw/i386/multiboot.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c index b9064264d8..1e215bf8d3 100644 --- a/hw/i386/multiboot.c +++ b/hw/i386/multiboot.c @@ -247,6 +247,10 @@ 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"); -- 2.13.6