s390/ctcm: Fix timer corruption in fsm_addtimer()

fsm_addtimer() calls timer_setup() unconditionally before add_timer().
If called on an already-pending timer, timer_setup() re-initializes
the timer's list_head fields while the timer is still enqueued in the
wheel, corrupting the timer list.

The timer is already initialized once by fsm_settimer() which calls
timer_setup() correctly. Multiple callsites invoke fsm_addtimer()
without a preceding fsm_deltimer(), including ctcm_main.c
ctcmpc_send_sweep_req() and ctcm_mpc.c mpc_action_side_xid(), making the
redundant timer_setup() in fsm_addtimer() a real corruption risk.

Remove the redundant timer_setup() calls from fsm_addtimer() and
fsm_modtimer(), and replace add_timer() with mod_timer() which safely
handles both pending and non-pending timers atomically without
corrupting the timer wheel.

Cc: stable+noautosel@kernel.org # never worked
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260803182736.2356374-1-nagamani@linux.ibm.com?part=1
Reviewed-by: Aswin Karuvally <aswin@linux.ibm.com>
Tested-by: Aswin Karuvally <aswin@linux.ibm.com>
Signed-off-by: Nagamani PV <nagamani@linux.ibm.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260930070234.569500-2-nagamani@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions