qemu-kvm/kvm-ui-clipboard-mark-type-as-not-available-when-there-i.patch

From 4069f8f55d070b5a1eb2bf894a517ea9fb648bbd Mon Sep 17 00:00:00 2001
From: Jon Maloy <jmaloy@redhat.com>
Date: Tue, 5 Mar 2024 11:36:15 -0500
Subject: [PATCH 2/3] ui/clipboard: mark type as not available when there is no
 data
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RH-Author: Jon Maloy <jmaloy@redhat.com>
RH-MergeRequest: 353: ui/clipboard: mark type as not available when there is no data
RH-Jira: RHEL-19628
RH-Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
RH-Acked-by: Gerd Hoffmann <None>
RH-Commit: [2/2] fa0edf7a362a16978e2377cf61f36ff227d186b2 (redhat/rhel/src/qemu-kvm/jons-qemu-kvm-2)

JIRA: https://issues.redhat.com/browse/RHEL-19628
CVE: CVE-2023-6683
Upstream: Merged
Conflicts:
         - The function g_memdup2() is used by this commit, but is not present in
           this code version. It looks safe to introduce it in a preceding commit,
           instead of reverting to the less safe g_memdup(), so that is what we do.
         - There is a second upstream commit covering this CVE:
           commit 9c416582611b ("ui/clipboard: add asserts for update and request")
           which is based on several other previous commits not present in this version.
           Re-applying these, or trying to adapt the code, is too intrusive and risky
           given that it only introduces two diagnostic asserts which are not essential
           for solving the CVE.
           We therefore omit that commit.

commit 405484b29f6548c7b86549b0f961b906337aa68a
Author: Fiona Ebner <f.ebner@proxmox.com>
Date:   Wed Jan 24 11:57:48 2024 +0100

    ui/clipboard: mark type as not available when there is no data

    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>

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 ui/clipboard.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/ui/clipboard.c b/ui/clipboard.c
index d7b008d62a..b8c795f2e2 100644
--- a/ui/clipboard.c
+++ b/ui/clipboard.c
@@ -123,9 +123,15 @@ 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);
-- 
2.41.0