[Qemu-devel] [PATCH 1/5] multiboot: Reject kernels exceeding the address space

[Kevin Wolf <kwolf@redhat.com>]

The code path with a manually set mh_load_addr in the Multiboot header
checks that load_end_addr <= load_addr, but the path where load_end_addr
is automatically detected if 0 is given in the header misses the
corresponding check. 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 <kwolf@redhat.com>
---
 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