hw/core/loader: Fix possible crash in rom_copy()
authorThomas Huth <thuth@redhat.com>
Wed, 25 Sep 2019 12:16:43 +0000 (14:16 +0200)
committerThomas Huth <thuth@redhat.com>
Tue, 1 Oct 2019 09:42:27 +0000 (11:42 +0200)
commite423455c4f23a1a828901c78fe6d03b7dde79319
tree7bb7f8e2f80f94ec823570f507ee030c46b460bb
parentcd4fc142074f47fdcc850676a13d29bb3facc100
hw/core/loader: Fix possible crash in rom_copy()

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-stable@nongnu.org
Reported-by: Guangming Liu
Buglink: https://bugs.launchpad.net/qemu/+bug/1844635
Message-Id: <20190925130331.27825-1-thuth@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
hw/core/loader.c