xwayland: fix CVE-2025-49178

A flaw was found in the X server's request handling. Non-zero 'bytes to ignore'
in a client's request can cause the server to skip processing another client's
request, potentially leading to a denial of service.

(From OE-Core rev: 4c6df8320497c2ebf09902a62b6a3f3b061be917)

Signed-off-by: Archana Polampalli <archana.polampalli@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/recipes-graphics/xwayland/xwayland/CVE-2025-49178.patch

@@ -0,0 +1,50 @@
+From d55c54cecb5e83eaa2d56bed5cc4461f9ba318c2 Mon Sep 17 00:00:00 2001
+From: Olivier Fourdan <ofourdan@redhat.com>
+Date: Mon, 28 Apr 2025 10:46:03 +0200
+Subject: [PATCH] os: Account for bytes to ignore when sharing input buffer
+
+When reading requests from the clients, the input buffer might be shared
+and used between different clients.
+
+If a given client sends a full request with non-zero bytes to ignore,
+the bytes to ignore may still be non-zero even though the request is
+full, in which case the buffer could be shared with another client who's
+request will not be processed because of those bytes to ignore, leading
+to a possible hang of the other client request.
+
+To avoid the issue, make sure we have zero bytes to ignore left in the
+input request when sharing the input buffer with another client.
+
+CVE-2025-49178
+
+This issue was discovered by Nils Emmerich <nemmerich@ernw.de> and
+reported by Julian Suleder via ERNW Vulnerability Disclosure.
+
+Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
+Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
+Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2024>
+
+CVE: CVE-2025-49178
+
+Upstream-Status: Backport [https://gitlab.freedesktop.org/xorg/xserver/-/commit/d55c54cecb5e83eaa2d56bed5cc4461f9ba318c2]
+
+Signed-off-by: Archana Polampalli <archana.polampalli@windriver.com>
+---
+ os/io.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/os/io.c b/os/io.c
+index 67465f9..f92a40e 100644
+--- a/os/io.c
++++ b/os/io.c
+@@ -444,7 +444,7 @@ ReadRequestFromClient(ClientPtr client)
+      */
+
+     gotnow -= needed;
+-    if (!gotnow)
++    if (!gotnow && !oci->ignoreBytes)
+         AvailableInput = oc;
+     if (move_header) {
+         if (client->req_len < bytes_to_int32(sizeof(xBigReq) - sizeof(xReq))) {
+--
+2.40.0

meta/recipes-graphics/xwayland/xwayland_23.2.5.bb

@@ -28,6 +28,7 @@ SRC_URI = "https://www.x.org/archive/individual/xserver/xwayland-${PV}.tar.xz \
            file://CVE-2025-49176-0001.patch \
            file://CVE-2025-49176-0002.patch \
            file://CVE-2025-49177.patch \
+           file://CVE-2025-49178.patch \
 "
 SRC_URI[sha256sum] = "33ec7ff2687a59faaa52b9b09aa8caf118e7ecb6aed8953f526a625ff9f4bd90"