40b9b28df1
hw/block/fdc: Extract blk_create_empty_drive() hw/block/fdc: Kludge missing floppy drive to fix CVE-2021-20196 tests/fdc-test: Add a regression test for CVE-2021-20196 display/qxl-render: fix race condition in qxl_cursor (CVE-2021-4207) ui/cursor: fix integer overflow in cursor_alloc (CVE-2021-4206) Signed-off-by: yezengruan <yezengruan@huawei.com> Signed-off-by: bobychen <boby.chen@huawei.com>
63 lines
2.3 KiB
Diff
63 lines
2.3 KiB
Diff
From c303ae575659493d747225f61430460dec809362 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@redhat.com>
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Date: Wed, 24 Nov 2021 17:15:35 +0100
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Subject: [PATCH 2/5] hw/block/fdc: Kludge missing floppy drive to fix
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CVE-2021-20196
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Guest might select another drive on the bus by setting the
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DRIVE_SEL bit of the DIGITAL OUTPUT REGISTER (DOR).
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The current controller model doesn't expect a BlockBackend
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to be NULL. A simple way to fix CVE-2021-20196 is to create
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an empty BlockBackend when it is missing. All further
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accesses will be safely handled, and the controller state
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machines keep behaving correctly.
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Cc: qemu-stable@nongnu.org
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Fixes: CVE-2021-20196
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Reported-by: Gaoning Pan (Ant Security Light-Year Lab) <pgn@zju.edu.cn>
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Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
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Reviewed-by: Hanna Reitz <hreitz@redhat.com>
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Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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Message-id: 20211124161536.631563-3-philmd@redhat.com
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BugLink: https://bugs.launchpad.net/qemu/+bug/1912780
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/338
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Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
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Reviewed-by: Hanna Reitz <hreitz@redhat.com>
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Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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Signed-off-by: John Snow <jsnow@redhat.com>
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---
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hw/block/fdc.c | 14 +++++++++++++-
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1 file changed, 13 insertions(+), 1 deletion(-)
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diff --git a/hw/block/fdc.c b/hw/block/fdc.c
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index deea339d70..47b6939d44 100644
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--- a/hw/block/fdc.c
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+++ b/hw/block/fdc.c
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@@ -1358,7 +1358,19 @@ static FDrive *get_drv(FDCtrl *fdctrl, int unit)
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static FDrive *get_cur_drv(FDCtrl *fdctrl)
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{
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- return get_drv(fdctrl, fdctrl->cur_drv);
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+ FDrive *cur_drv = get_drv(fdctrl, fdctrl->cur_drv);
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+
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+ if (!cur_drv->blk) {
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+ /*
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+ * Kludge: empty drive line selected. Create an anonymous
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+ * BlockBackend to avoid NULL deref with various BlockBackend
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+ * API calls within this model (CVE-2021-20196).
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+ * Due to the controller QOM model limitations, we don't
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+ * attach the created to the controller device.
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+ */
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+ cur_drv->blk = blk_create_empty_drive();
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+ }
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+ return cur_drv;
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}
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/* Status A register : 0x00 (read-only) */
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--
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2.27.0
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