File _service:tar_scm:backport-CVE-2023-24626.patch of Package screen

File _service:tar_scm:backport-CVE-2023-24626.patch of Package screen (Revision 0f7ef29674e302602118f94bd18cb997)

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From 6df4a48ff6b31bedc2d0216b84dbe66cf9ca5e23 Mon Sep 17 00:00:00 2001
From: Alexander Naumov <alexander_naumov@opensuse.org>
Date: Wed, 1 Feb 2023 13:47:57 +0200
Subject: [PATCH] Missing signal sending permission check on failed query
 messages

When run as setuid root, one can send a query message to the
privileged screen process via its unix socket in order to force
it to send SIGHUP to a PID that can be freely specified in the
query packet.
Processes that do not explicitly handle SIGHUP will simply terminate

Signed-off-by: Alexander Naumov <alexander_naumov@opensuse.org>
---
 socket.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/socket.c b/socket.c
index bb68b35..0a575cf 100644
--- a/socket.c
+++ b/socket.c
@@ -1285,11 +1285,16 @@ ReceiveMsg()
           else
             queryflag = -1;
 
-          Kill(m.m.command.apid,
+	  if (CheckPid(m.m.command.apid)) {
+	    Msg(0, "Query attempt with bad pid(%d)!", m.m.command.apid);
+	  }
+	  else {
+            Kill(m.m.command.apid,
                (queryflag >= 0)
                    ? SIGCONT
                    : SIG_BYE); /* Send SIG_BYE if an error happened */
-          queryflag = -1;
+            queryflag = -1;
+	  }
         }
         break;
       case MSG_COMMAND:
-- 
2.27.0