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Fri, 17 Jul 2026 11:53:14 +0000 (UTC) Received: from localhost (unknown [10.44.22.17]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id DBDF8180034C for ; Fri, 17 Jul 2026 11:53:13 +0000 (UTC) From: =?utf-8?q?Marc-Andr=C3=A9_Lureau?= Date: Fri, 17 Jul 2026 15:52:41 +0400 Subject: [GIT PULL 02/15] ui/vnc: fix OOB write in vnc_refresh_lossy_rect MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20260717-fix-v1-2-cb9f7d49dc52@redhat.com> References: <20260717-fix-v1-0-cb9f7d49dc52@redhat.com> In-Reply-To: <20260717-fix-v1-0-cb9f7d49dc52@redhat.com> To: qemu-devel@nongnu.org X-Developer-Signature: v=1; a=openpgp-sha256; l=2067; i=marcandre.lureau@redhat.com; h=from:subject:message-id; bh=d9iNnmvHwz9V5eb/jktzHMJMRQuIJZmRJLaiZr8hjbc=; b=owEBbQKS/ZANAwAKAdro4Ql1lpzlAcsmYgBqWheZIcuGkn26LiPnDDQ9Py5Q73jtihRboQE+U f1umep+Qv+JAjMEAAEKAB0WIQSHqb2TP4fGBtJ29i3a6OEJdZac5QUCaloXmQAKCRDa6OEJdZac 5b0OEACGtbJ/thrBFKZ1F1XYfmvdONWJUWbW7O77XtXr1X39W/WXC/oBd2mU7yY7fW27fLdE+C9 1gb4bMDQM7ZXXKyrUOqb+85xSz4+CYXyAZAl0JMuf3XD0zW7sWN+8v7PZbMjVkTlEUZ2GVDebJ0 cplqd7B7NpsH3/L8gIS2QFT1Ue+Wc3y2lu9QCrFmuCU9v2HoSJUYlW7qaluv1/VMlsKc/WWjY6D gjyyMID6E/4iDA8Bs3mbcFrY02QvHu9YE6/q4MO1LO5Y4Ul6IPzQejeLU91GTVVXA3lskthbPpm e8Kon9ohyWQFVfmmvhsgeoXkfvbSLtOQdQITI9Umzdoi/t4iIS39nT2fq7N4fwrQAjLKL6KjEtA NZjk1YszxecN68H6MOEtu88v+83hwQ679i3WRsLPMDiLVJ8ywLX7TtAWoegE691+T2F3ZQ90hiv tYmzF6FQH6LG9m0Z6PMQ5ieKR8qXVayRhzbOWQKJeTqYXSw/cXEfuMWl2K4TAJeiBxuxLBG6SHX TSCWBYXIRkuLoK+U8bAuafg+anOmBjs5C3gY9jTe1xdziYeVcZKAm7B+cUO2Cm79nuzur2yi8ZN kcQn7mFPx+to8z6p2zvkGbWKC9zAmRuSPdpEW7eCs6u06BzIsLDkrIf0QeW/SvD5kuDjNb6Tx9A 4eDBTFaF0cM5G6w== X-Developer-Key: i=marcandre.lureau@redhat.com; a=openpgp; fpr=87A9BD933F87C606D276F62DDAE8E10975969CE5 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Received-SPF: permerror client-ip=170.10.129.124; envelope-from=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.01, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org vnc_refresh_lossy_rect() always marks a full VNC_STAT_RECT (64) rows as dirty when refreshing a lossy tile. When the display height is not a multiple of VNC_STAT_RECT (e.g. VNC_MAX_HEIGHT = 2160), the bottom tile is partial -- the last tile at y=2112 has only 48 valid rows. The unclamped loop writes to vs->dirty[2160..2175], past the end of the VNC_MAX_HEIGHT-sized array. Clamp the row count to the actual surface height so partial bottom tiles only mark valid dirty bitmap entries. Fixes: CVE-2026-48002 Fixes: 7d964c9d2fc6 ("vnc: refresh lossy rect after a given timeout") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3950 Reported-by: huntr bubble Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Marc-Andre Lureau --- ui/vnc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/ui/vnc.c b/ui/vnc.c index b2b69923b75..559d3954b87 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -3004,10 +3004,18 @@ static int vnc_refresh_lossy_rect(VncDisplay *vd, int x, int y) int sty = y / VNC_STAT_RECT; int stx = x / VNC_STAT_RECT; int has_dirty = 0; + int height = MIN(pixman_image_get_height(vd->guest.fb), + pixman_image_get_height(vd->server)); + int rows; y = QEMU_ALIGN_DOWN(y, VNC_STAT_RECT); x = QEMU_ALIGN_DOWN(x, VNC_STAT_RECT); + rows = MIN(VNC_STAT_RECT, height - y); + if (rows <= 0) { + return 0; + } + QTAILQ_FOREACH(vs, &vd->clients, next) { VncConnection *vc = container_of(vs, VncConnection, vs); int j; @@ -3022,7 +3030,7 @@ static int vnc_refresh_lossy_rect(VncDisplay *vd, int x, int y) } vc->worker.lossy_rect[sty][stx] = 0; - for (j = 0; j < VNC_STAT_RECT; ++j) { + for (j = 0; j < rows; ++j) { bitmap_set(vs->dirty[y + j], x / VNC_DIRTY_PIXELS_PER_BIT, VNC_STAT_RECT / VNC_DIRTY_PIXELS_PER_BIT); -- 2.55.0