Both, "rom->addr" and "addr" are derived from the binary image
that can be loaded with the "-kernel" paramer. The code in
rom_copy() then calculates:
d = dest + (rom->addr - addr);
and uses "d" as destination in a memcpy() some lines later. Now with
bad kernel images, it is possible that rom->addr is smaller than addr,
thus "rom->addr - addr" gets negative and the memcpy() then tries to
copy contents from the image to a bad memory location. This could
maybe be used to inject code from a kernel image into the QEMU binary,
so we better fix it with an additional sanity check here.
Cc: qemu-sta...@nongnu.org
Reported-by: Guangming Liu
Buglink: https://bugs.launchpad.net/qemu/+bug/1844635
Message-Id: <20190925130331.27825-1-th...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Thomas Huth <th...@redhat.com>
---
hw/core/loader.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/core/loader.c b/hw/core/loader.c
index 0d60219364..5099f27dc8 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -1281,7 +1281,7 @@ int rom_copy(uint8_t *dest, hwaddr addr, size_t size)
if (rom->addr + rom->romsize < addr) {
continue;
}
- if (rom->addr > end) {
+ if (rom->addr > end || rom->addr < addr) {
break;
}
--
2.18.1
