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Re: [Qemu-devel] [PATCH v3] loader: Check access size when calling rom_p
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH v3] loader: Check access size when calling rom_ptr() to avoid crashes |
Date: |
Fri, 15 Jun 2018 11:59:09 +0200 |
On Fri, 15 Jun 2018 11:49:05 +0200
Thomas Huth <address@hidden> wrote:
> The rom_ptr() function allows direct access to the ROM blobs that we
> load during startup. However, there are currently no checks for the
> size of the accesses, so it's currently possible to crash QEMU for
> example with:
>
> $ echo "Insane in the mainframe" > /tmp/test.txt
> $ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -append xyz
> Segmentation fault (core dumped)
> $ s390x-softmmu/qemu-system-s390x -kernel /tmp/test.txt -initrd /tmp/test.txt
> Segmentation fault (core dumped)
> $ echo -n HdrS > /tmp/hdr.txt
> $ sparc64-softmmu/qemu-system-sparc64 -kernel /tmp/hdr.txt -initrd
> /tmp/hdr.txt
> Segmentation fault (core dumped)
>
> We need a possibility to check the size of the ROM area that we want
> to access, thus let's add a size parameter to the rom_ptr() function
> to avoid these problems.
>
> Signed-off-by: Thomas Huth <address@hidden>
> ---
> v3: Fix the check in find_rom()
>
> hw/core/loader.c | 10 +++++-----
> hw/mips/mips_malta.c | 6 ++++--
> hw/s390x/ipl.c | 13 ++++++++++---
> hw/sparc/sun4m.c | 4 ++--
> hw/sparc64/sun4u.c | 4 ++--
> include/hw/loader.h | 2 +-
> target/arm/cpu.c | 2 +-
> 7 files changed, 25 insertions(+), 16 deletions(-)
> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> index 04245b5..bcac204 100644
> --- a/hw/s390x/ipl.c
> +++ b/hw/s390x/ipl.c
> @@ -195,8 +199,11 @@ static void s390_ipl_realize(DeviceState *dev, Error
> **errp)
> * we have to overwrite values in the kernel image,
> * which are "rom"
> */
> - stq_p(rom_ptr(INITRD_PARM_START), initrd_offset);
> - stq_p(rom_ptr(INITRD_PARM_SIZE), initrd_size);
> + romptr = rom_ptr(INITRD_PARM_START, 16);
> + if (romptr) {
> + stq_p(romptr, initrd_offset);
> + stq_p(romptr + 1, initrd_size);
INITRD_PARM_SIZE seems to be unused now. We can remove it in a separate
patch if you don't respin, though.
> + }
> }
> }
> /*
Reviewed-by: Cornelia Huck <address@hidden>