From 7b439d25300dc59bba76b53eb344bb9e5a1133f2 Mon Sep 17 00:00:00 2001 From: Carsten Otte Date: Tue, 10 Jun 2008 10:03:22 +0200 Subject: [PATCH] [S390] vt220 console, initialize list head before use This patch fixes a null pointer dereference during initialisation when no sclp event facility is available: sclp vt220 tty driver: could not register vt220 - sclp_register returned -5 Unable to handle kernel paging request at virtual user address 0000000000000000 Oops: 0004 [#1] PREEMPT SMP Modules linked in: CPU: 0 Not tainted 2.6.26-rc3-kvm-bigiron-00968-gd939e93-dirty #30 Process swapper (pid: 0, task: 0000000000600be0, ksp: 000000000064a000) Krnl PSW : 0400000180000000 0000000000320d8c (sclp_unregister+0x48/0x8c) R:0 T:1 IO:0 EX:0 Key:0 M:0 W:0 P:0 AS:0 CC:0 PM:0 EA:3 Krnl GPRS: 0000000000000000 0000000000000000 0000000000630478 0700000000649c20 0000000000000000 0000000000433060 000000000064a660 0000000002e26000 00000000006db000 0000000000000000 0000000000a78578 0000000000649b80 0000000000630dc0 000000000044fa20 0000000000320d76 0000000000649b80 Krnl Code: 0000000000320d7c: e310c0080004 lg %r1,8(%r12) 0000000000320d82: b9040032 lgr %r3,%r2 0000000000320d86: c02000187b79 larl %r2,630478 >0000000000320d8c: e34010000024 stg %r4,0(%r1) 0000000000320d92: e31040080024 stg %r1,8(%r4) 0000000000320d98: c01100200200 lgfi %r1,2097664 0000000000320d9e: e310c0080024 stg %r1,8(%r12) 0000000000320da4: c01100100100 lgfi %r1,1048832 Call Trace: ([<0000000000320d76>] sclp_unregister+0x32/0x8c) [<00000000006657b4>] __sclp_vt220_cleanup+0xc4/0xe0 [<000000000066595c>] __sclp_vt220_init+0x18c/0x1a0 [<0000000000665aba>] sclp_vt220_con_init+0x42/0x68 [<00000000006601ca>] console_init+0x4e/0x68 [<000000000064acae>] start_kernel+0x3a2/0x4dc [<0000000000100020>] _stext+0x20/0x80 INFO: lockdep is turned off. Last Breaking-Event-Address: [<000000000041f964>] _spin_lock_irqsave+0xb0/0xb4 <4>---[ end trace 31fd0ba7d8756001 ]--- The issue is caused by a list_empty() check in __sclp_vt220_cleanup, which usually fails on non-initialized list heads that contain {NULL,NULL} instead. Signed-off-by: Carsten Otte Signed-off-by: Martin Schwidefsky --- drivers/s390/char/sclp_vt220.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/s390/char/sclp_vt220.c b/drivers/s390/char/sclp_vt220.c index 62576af36f..3e577f655b 100644 --- a/drivers/s390/char/sclp_vt220.c +++ b/drivers/s390/char/sclp_vt220.c @@ -773,6 +773,7 @@ sclp_vt220_con_init(void) { int rc; + INIT_LIST_HEAD(&sclp_vt220_register.list); if (!CONSOLE_IS_SCLP) return 0; rc = __sclp_vt220_init(); -- 2.39.5