[PATCH 42/55] hw/core/loader: Fix possible crash in rom_copy()

[Michael Roth]

From: Thomas Huth <address@hidden>

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: address@hidden
Reported-by: Guangming Liu
Buglink: https://bugs.launchpad.net/qemu/+bug/1844635
Message-Id: <address@hidden>
Reviewed-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Thomas Huth <address@hidden>
(cherry picked from commit e423455c4f23a1a828901c78fe6d03b7dde79319)
Signed-off-by: Michael Roth <address@hidden>
---
 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 425bf69a99..838a34174a 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -1242,7 +1242,7 @@ 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;
         }
 
-- 
2.17.1