On Tue, Nov 29, 2022 at 1:08 AM vkumbhar <[email protected]> wrote:
>
> From: Vivek Kumbhar <[email protected]>
>
> Upstream-Status: Backport 
> [https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233]
>
> Signed-off-by: Vivek Kumbhar <[email protected]>
> ---
>  meta/recipes-devtools/qemu/qemu.inc           |  1 +
>  .../qemu/qemu/CVE-2021-20196.patch            | 62 +++++++++++++++++++
>  2 files changed, 63 insertions(+)
>  create mode 100644 meta/recipes-devtools/qemu/qemu/CVE-2021-20196.patch
>
> diff --git a/meta/recipes-devtools/qemu/qemu.inc 
> b/meta/recipes-devtools/qemu/qemu.inc
> index 764f948a28..a915b54c1a 100644
> --- a/meta/recipes-devtools/qemu/qemu.inc
> +++ b/meta/recipes-devtools/qemu/qemu.inc
> @@ -113,6 +113,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
>             file://CVE-2022-0216-2.patch \
>             file://CVE-2021-3750.patch \
>            file://CVE-2021-3638.patch \
> +          file://CVE-2021-20196.patch \
>             "
>  UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"
>
> diff --git a/meta/recipes-devtools/qemu/qemu/CVE-2021-20196.patch 
> b/meta/recipes-devtools/qemu/qemu/CVE-2021-20196.patch
> new file mode 100644
> index 0000000000..24da80e7db
> --- /dev/null
> +++ b/meta/recipes-devtools/qemu/qemu/CVE-2021-20196.patch
> @@ -0,0 +1,62 @@
> +From 94608c59045791dfd35102bc59b792e96f2cfa30 Mon Sep 17 00:00:00 2001
> +From: Vivek Kumbhar <[email protected]>
> +Date: Tue, 29 Nov 2022 15:57:13 +0530
> +Subject: [PATCH] CVE-2021-20196
> +
> +Upstream-Status: 
> https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233

This should be: Upstream-Status: Backport
[https://gitlab.com/qemu-project/qemu/-/commit/1ab95af033a419e7a64e2d58e67dd96b20af5233]

I've fixed it, so no need for a v2.

Steve

> +CVE: CVE-2021-20196
> +Signed-off-by: Vivek Kumbhar <[email protected]>
> +
> +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.
> +---
> + hw/block/fdc.c | 19 ++++++++++++++++++-
> + 1 file changed, 18 insertions(+), 1 deletion(-)
> +
> +diff --git a/hw/block/fdc.c b/hw/block/fdc.c
> +index ac5d31e8..e128e975 100644
> +--- a/hw/block/fdc.c
> ++++ b/hw/block/fdc.c
> +@@ -58,6 +58,11 @@
> +         }                                                       \
> +     } while (0)
> +
> ++/* Anonymous BlockBackend for empty drive */
> ++static BlockBackend *blk_create_empty_drive(void)
> ++{
> ++    return blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);
> ++}
> +
> + /********************************************************/
> + /* qdev floppy bus                                      */
> +@@ -1356,7 +1361,19 @@ 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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