[PATCH net v2] s390/ctcm: Prevent XID null dereference
From: Aswin Karuvally <aswin@linux.ibm.com>
Date: 2026-08-27 06:34:21
Also in:
linux-s390, stable
Subsystem:
networking drivers, s390 architecture, s390 network drivers, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, Alexandra Winter, Aswin Karuvally, Linus Torvalds
The mpc_validate_xid() function sets grp->saved_xid2->xid2_flag2 to 0x40
to signal XID validation error. If peer XID is NULL or r/w channel
pairing mismatch happens, grp->saved_xid2 is never initialized. An
attempt to set the flag in such case leads to NULL dereference.
Fix this by using the always available priv->xid->xid2_flag2 instead of
grp->saved_xid2->xid2_flag2 for validation errors.
Fixes: 293d984f0e36 ("ctcm: infrastructure for replaced ctc driver")
Cc: stable@vger.kernel.org
Signed-off-by: Aswin Karuvally <aswin@linux.ibm.com>
---
Changes in v2:
* Ensure FSM goes to INOP for XID validation failure of either channel
drivers/s390/net/ctcm_mpc.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/s390/net/ctcm_mpc.c b/drivers/s390/net/ctcm_mpc.c
index 08e36685e578..61c88fe853c5 100644
--- a/drivers/s390/net/ctcm_mpc.c
+++ b/drivers/s390/net/ctcm_mpc.c@@ -826,7 +826,7 @@ static void mpc_action_go_ready(fsm_instance *fsm, int event, void *arg) fsm_deltimer(&grp->timer); - if (grp->saved_xid2->xid2_flag2 == 0x40) { + if (priv->xid->xid2_flag2 == 0x40) { priv->xid->xid2_flag2 = 0x00; if (grp->estconnfunc) { grp->estconnfunc(grp->port_num, 1,
@@ -1636,7 +1636,6 @@ static int mpc_validate_xid(struct mpcg_info *mpcginfo) "The XID used in the MPC protocol is not valid, " "rc = %d\n", rc); priv->xid->xid2_flag2 = 0x40; - grp->saved_xid2->xid2_flag2 = 0x40; } return rc;
base-commit: f967455fb2a5a2079b9eb5823e9ccf359174bf9f -- 2.53.0