[dunfell] qemu: fix CVE-2021-20196

Source: https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233
MR: 111637
Type: Security Fix
Disposition: Backport from https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233
ChangeID: c1e435aa25bb60b362bb68ab253ff55504e0328d
Description:
    hw/block/fdc: Kludge missing floppy drive to fix CVE-2021-20196

    Guest might select another drive on the bus by setting the
    DRIVE_SEL bit of the DIGITAL OUTPUT REGISTER (DOR).
    The current controller model doesn't expect a BlockBackend
    to be NULL. A simple way to fix CVE-2021-20196 is to create
    an empty BlockBackend when it is missing. All further
    accesses will be safely handled, and the controller state
    machines keep behaving correctly.

Signed-off-by: Vivek Kumbhar <vkumbhar@mvista.com>
---
 meta/recipes-devtools/qemu/qemu.inc           |  1 +
 .../qemu/qemu/0001-CVE-2021-20196.patch       | 40 +++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 meta/recipes-devtools/qemu/qemu/0001-CVE-2021-20196.patch

On Tue, Oct 11, 2022 at 5:05 AM vkumbhar <vkumbhar@mvista.com> wrote:
>
> Source: https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233
> MR: 111637
> Type: Security Fix
> Disposition: Backport from https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233
> ChangeID: c1e435aa25bb60b362bb68ab253ff55504e0328d
> Description:
>     hw/block/fdc: Kludge missing floppy drive to fix CVE-2021-20196
>
>     Guest might select another drive on the bus by setting the
>     DRIVE_SEL bit of the DIGITAL OUTPUT REGISTER (DOR).
>     The current controller model doesn't expect a BlockBackend
>     to be NULL. A simple way to fix CVE-2021-20196 is to create
>     an empty BlockBackend when it is missing. All further
>     accesses will be safely handled, and the controller state
>     machines keep behaving correctly.
>
> Signed-off-by: Vivek Kumbhar <vkumbhar@mvista.com>
> ---
>  meta/recipes-devtools/qemu/qemu.inc           |  1 +
>  .../qemu/qemu/0001-CVE-2021-20196.patch       | 40 +++++++++++++++++++
>  2 files changed, 41 insertions(+)
>  create mode 100644 meta/recipes-devtools/qemu/qemu/0001-CVE-2021-20196.patch

Again, please name the file CVE-2021-20196.patch

>
> diff --git a/meta/recipes-devtools/qemu/qemu.inc b/meta/recipes-devtools/qemu/qemu.inc
> index 7a963ad57c..2cdb718b1f 100644
> --- a/meta/recipes-devtools/qemu/qemu.inc
> +++ b/meta/recipes-devtools/qemu/qemu.inc
> @@ -52,6 +52,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
>            file://CVE-2019-20175.patch \
>            file://CVE-2020-24352.patch \
>            file://CVE-2020-25723.patch \
> +          file://0001-CVE-2021-20196.patch \

Same issue here, you are not using current dunfell head so this patch
doesn't apply.

Please rebase on current dunfell head and send a V2.

Thanks!

Steve

>            "
>  UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"
>
> diff --git a/meta/recipes-devtools/qemu/qemu/0001-CVE-2021-20196.patch b/meta/recipes-devtools/qemu/qemu/0001-CVE-2021-20196.patch
> new file mode 100644
> index 0000000000..affc8ead58
> --- /dev/null
> +++ b/meta/recipes-devtools/qemu/qemu/0001-CVE-2021-20196.patch
> @@ -0,0 +1,40 @@
> +From a253e632aea9e0e3f3f2ad3d157f34908e9c2008 Mon Sep 17 00:00:00 2001
> +From: Vivek Kumbhar <vkumbhar@mvista.com>
> +Date: Mon, 10 Oct 2022 10:00:53 +0530
> +Subject: [PATCH] CVE-2021-20196
> +
> +Upstream-Status: https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233
> +CVE: CVE-2021-20196
> +Signed-off-by: Vivek Kumbhar <vkumbhar@mvista.com>
> +---
> + hw/block/fdc.c | 14 +++++++++++++-
> + 1 file changed, 13 insertions(+), 1 deletion(-)
> +
> +diff --git a/hw/block/fdc.c b/hw/block/fdc.c
> +index ac5d31e8..a887369c 100644
> +--- a/hw/block/fdc.c
> ++++ b/hw/block/fdc.c
> +@@ -1356,7 +1356,19 @@ static FDrive *get_drv(FDCtrl *fdctrl, int unit)
> +
> + static FDrive *get_cur_drv(FDCtrl *fdctrl)
> + {
> +-    return get_drv(fdctrl, fdctrl->cur_drv);
> ++    FDrive *cur_drv = get_drv(fdctrl, fdctrl->cur_drv);
> ++
> ++    if (!cur_drv->blk) {
> ++        /*
> ++         * Kludge: empty drive line selected. Create an anonymous
> ++         * BlockBackend to avoid NULL deref with various BlockBackend
> ++         * API calls within this model (CVE-2021-20196).
> ++         * Due to the controller QOM model limitations, we don't
> ++         * attach the created to the controller device.
> ++         */
> ++        cur_drv->blk = blk_create_empty_drive();
> ++    }
> ++    return cur_drv;
> + }
> +
> + /* Status A register : 0x00 (read-only) */
> +--
> +2.25.1
> +
> --
> 2.25.1
>
>
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