Hi Kevin.
My comments are inline...
On 2018-03-14 10:32, Kevin Wolf wrote:
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.
1) The code checks that load_end_addr >= load_addr (before letting it
through).
2) load_end_addr is used only when it is read in as non-zero, so no
check is needed if zero. (It gets debug-printed even when zero, but is
used only to calculate mb_load_size and only when non-zero.)
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.
Code itself looks fine.
Modulo above comments:
Reviewed-by: Jack Schwartz <jack.schwa...@oracle.com>
Thanks,
Jack
Signed-off-by: Kevin Wolf <kw...@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");
