qemu: fix CVE-2023-42467

QEMU through 8.0.0 could trigger a division by zero in scsi_disk_reset
in hw/scsi/scsi-disk.c because scsi_disk_emulate_mode_select does not
prevent s->qdev.blocksize from being 256. This stops QEMU and the guest
immediately.

References:
https://nvd.nist.gov/vuln/detail/CVE-2023-42467
https://gitlab.com/qemu-project/qemu/-/issues/1813

(From OE-Core rev: 7c42b976d7a72acf917bae9d055768a1350e507d)

Signed-off-by: Yogita Urade <yogita.urade@windriver.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 50 insertions, 0 deletions

diff --git a/meta/recipes-devtools/qemu/qemu.inc b/meta/recipes-devtools/qemu/qemu.inc
index 9664b747b3..b331f87c0d 100644
--- a/meta/recipes-devtools/qemu/qemu.inc
+++ b/meta/recipes-devtools/qemu/qemu.inc
@@ -35,6 +35,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
            file://fixmips.patch \
            file://qemu-guest-agent.init \
            file://qemu-guest-agent.udev \
+           file://CVE-2023-42467.patch \
            "
 UPSTREAM_CHECK_REGEX = "qemu-(?P<pver>\d+(\.\d+)+)\.tar"
 
diff --git a/meta/recipes-devtools/qemu/qemu/CVE-2023-42467.patch b/meta/recipes-devtools/qemu/qemu/CVE-2023-42467.patch
new file mode 100644
index 0000000000..86ab7cf81a
--- /dev/null
+++ b/meta/recipes-devtools/qemu/qemu/CVE-2023-42467.patch
@@ -0,0 +1,49 @@
+From 7cfcc79b0ab800959716738aff9419f53fc68c9c Mon Sep 17 00:00:00 2001
+From: Thomas Huth <thuth@redhat.com>
+Date: Thu, 5 Oct 2023 06:01:10 +0000
+Subject: [PATCH] hw/scsi/scsi-disk: Disallow block sizes smaller than 512
+ [CVE-2023-42467]
+
+We are doing things like
+
+    nb_sectors /= (s->qdev.blocksize / BDRV_SECTOR_SIZE);
+
+in the code here (e.g. in scsi_disk_emulate_mode_sense()), so if
+the blocksize is smaller than BDRV_SECTOR_SIZE (=512), this crashes
+with a division by 0 exception. Thus disallow block sizes of 256
+bytes to avoid this situation.
+
+Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1813
+CVE: 2023-42467
+Signed-off-by: Thomas Huth <thuth@redhat.com>
+Message-ID: <20230925091854.49198-1-thuth@redhat.com>
+Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
+
+CVE: CVE-2023-42467
+
+Upstream-Status: Backport [https://gitlab.com/qemu-project/qemu/-/commit/7cfcc79b0ab800959716738aff9419f53fc68c9c]
+
+Signed-off-by: Yogita Urade <yogita.urade@windriver.com>
+---
+ hw/scsi/scsi-disk.c | 5 +++--
+ 1 file changed, 3 insertions(+), 2 deletions(-)
+
+diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
+index e0d79c796..477ee2bcd 100644
+--- a/hw/scsi/scsi-disk.c
++++ b/hw/scsi/scsi-disk.c
+@@ -1628,9 +1628,10 @@ static void scsi_disk_emulate_mode_select(SCSIDiskReq *r, uint8_t *inbuf)
+          * Since the existing code only checks/updates bits 8-15 of the block
+          * size, restrict ourselves to the same requirement for now to ensure
+          * that a block size set by a block descriptor and then read back by
+-         * a subsequent SCSI command will be the same
++         * a subsequent SCSI command will be the same. Also disallow a block
++         * size of 256 since we cannot handle anything below BDRV_SECTOR_SIZE.
+          */
+-        if (bs && !(bs & ~0xff00) && bs != s->qdev.blocksize) {
++        if (bs && !(bs & ~0xfe00) && bs != s->qdev.blocksize) {
+             s->qdev.blocksize = bs;
+             trace_scsi_disk_mode_select_set_blocksize(s->qdev.blocksize);
+         }
+--
+2.40.0