From: Kevin Wolf Date: Wed, 14 Mar 2018 16:46:38 +0000 (+0100) Subject: multiboot: Reject kernels exceeding the address space X-Git-Tag: qemu-xen-4.11.1^2~83 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=31b0eb0dad3daef6cd9eef74bc107cb3367450e7;p=qemu-xen.git multiboot: Reject kernels exceeding the address space 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: Michael Roth --- diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c index d9a0a95a2f..775aa5bfd0 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");