qemu: backport patch for ui/clipboard issue

Backported from upstream to fix CVE-2023-6683

(From OE-Core rev: d33a0ef657663faa05448454fad8a004879fe624)

Signed-off-by: Simone Weiß <simone.p.weiss@posteo.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/qemu/qemu.inc

@@ -39,6 +39,7 @@ SRC_URI = "https://download.qemu.org/${BPN}-${PV}.tar.xz \
            file://0003-linux-user-Add-strace-for-shmat.patch \
            file://0004-linux-user-Rewrite-target_shmat.patch \
            file://0005-tests-tcg-Check-that-shmat-does-not-break-proc-self-.patch \
+           file://CVE-2023-6683.patch \
            file://qemu-guest-agent.init \
            file://qemu-guest-agent.udev \
            "

meta/recipes-devtools/qemu/qemu/CVE-2023-6683.patch

@@ -0,0 +1,91 @@
+From 405484b29f6548c7b86549b0f961b906337aa68a Mon Sep 17 00:00:00 2001
+From: Fiona Ebner <f.ebner@proxmox.com>
+Date: Wed, 24 Jan 2024 11:57:48 +0100
+Subject: [PATCH] ui/clipboard: mark type as not available when there is no
+ data
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+With VNC, a client can send a non-extended VNC_MSG_CLIENT_CUT_TEXT
+message with len=0. In qemu_clipboard_set_data(), the clipboard info
+will be updated setting data to NULL (because g_memdup(data, size)
+returns NULL when size is 0). If the client does not set the
+VNC_ENCODING_CLIPBOARD_EXT feature when setting up the encodings, then
+the 'request' callback for the clipboard peer is not initialized.
+Later, because data is NULL, qemu_clipboard_request() can be reached
+via vdagent_chr_write() and vdagent_clipboard_recv_request() and
+there, the clipboard owner's 'request' callback will be attempted to
+be called, but that is a NULL pointer.
+
+In particular, this can happen when using the KRDC (22.12.3) VNC
+client.
+
+Another scenario leading to the same issue is with two clients (say
+noVNC and KRDC):
+
+The noVNC client sets the extension VNC_FEATURE_CLIPBOARD_EXT and
+initializes its cbpeer.
+
+The KRDC client does not, but triggers a vnc_client_cut_text() (note
+it's not the _ext variant)). There, a new clipboard info with it as
+the 'owner' is created and via qemu_clipboard_set_data() is called,
+which in turn calls qemu_clipboard_update() with that info.
+
+In qemu_clipboard_update(), the notifier for the noVNC client will be
+called, i.e. vnc_clipboard_notify() and also set vs->cbinfo for the
+noVNC client. The 'owner' in that clipboard info is the clipboard peer
+for the KRDC client, which did not initialize the 'request' function.
+That sounds correct to me, it is the owner of that clipboard info.
+
+Then when noVNC sends a VNC_MSG_CLIENT_CUT_TEXT message (it did set
+the VNC_FEATURE_CLIPBOARD_EXT feature correctly, so a check for it
+passes), that clipboard info is passed to qemu_clipboard_request() and
+the original segfault still happens.
+
+Fix the issue by handling updates with size 0 differently. In
+particular, mark in the clipboard info that the type is not available.
+
+While at it, switch to g_memdup2(), because g_memdup() is deprecated.
+
+Cc: qemu-stable@nongnu.org
+Fixes: CVE-2023-6683
+Reported-by: Markus Frank <m.frank@proxmox.com>
+Suggested-by: Marc-André Lureau <marcandre.lureau@redhat.com>
+Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
+Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
+Tested-by: Markus Frank <m.frank@proxmox.com>
+Message-ID: <20240124105749.204610-1-f.ebner@proxmox.com>
+
+CVE: CVE-2023-6683
+
+Upstream-Status: Backport [https://github.com/qemu/qemu/commit/405484b29f6548c7b86549b0f961b906337aa68a]
+Signed-off-by: Simone Weiß <simone.p.weiss@posteo.com>
+
+---
+ ui/clipboard.c | 12 +++++++++---
+ 1 file changed, 9 insertions(+), 3 deletions(-)
+
+diff --git a/ui/clipboard.c b/ui/clipboard.c
+index 3d14bffaf80f..b3f6fa3c9e1f 100644
+--- a/ui/clipboard.c
++++ b/ui/clipboard.c
+@@ -163,9 +163,15 @@ void qemu_clipboard_set_data(QemuClipboardPeer *peer,
+     }
+ 
+     g_free(info->types[type].data);
+-    info->types[type].data = g_memdup(data, size);
+-    info->types[type].size = size;
+-    info->types[type].available = true;
++    if (size) {
++        info->types[type].data = g_memdup2(data, size);
++        info->types[type].size = size;
++        info->types[type].available = true;
++    } else {
++        info->types[type].data = NULL;
++        info->types[type].size = 0;
++        info->types[type].available = false;
++    }
+ 
+     if (update) {
+         qemu_clipboard_update(info);