6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Harald Freudenberger <freude@xxxxxxxxxxxxx>
commit e14aec23025eeb1f2159ba34dbc1458467c4c347 upstream.
Fix kernel crash in AP bus code caused by very early invocation of the
config change callback function via SCLP.
After a fresh IML of the machine the crypto cards are still offline and
will get switched online only with activation of any LPAR which has the
card in it's configuration. A crypto card coming online is reported
to the LPAR via SCLP and the AP bus offers a callback function to get
this kind of information. However, it may happen that the callback is
invoked before the AP bus init function is complete. As the callback
triggers a synchronous AP bus scan, the scan may already run but some
internal states are not initialized by the AP bus init function resulting
in a crash like this:
[ 11.635859] Unable to handle kernel pointer dereference in virtual kernel address space
[ 11.635861] Failing address: 0000000000000000 TEID: 0000000000000887
[ 11.635862] Fault in home space mode while using kernel ASCE.
[ 11.635864] AS:00000000894c4007 R3:00000001fece8007 S:00000001fece7800 P:000000000000013d
[ 11.635879] Oops: 0004 ilc:1 [#1] SMP
[ 11.635882] Modules linked in:
[ 11.635884] CPU: 5 PID: 42 Comm: kworker/5:0 Not tainted 6.6.0-rc3-00003-g4dbf7cdc6b42 #12
[ 11.635886] Hardware name: IBM 3931 A01 751 (LPAR)
[ 11.635887] Workqueue: events_long ap_scan_bus
[ 11.635891] Krnl PSW : 0704c00180000000 0000000000000000 (0x0)
[ 11.635895] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
[ 11.635897] Krnl GPRS: 0000000001000a00 0000000000000000 0000000000000006 0000000089591940
[ 11.635899] 0000000080000000 0000000000000a00 0000000000000000 0000000000000000
[ 11.635901] 0000000081870c00 0000000089591000 000000008834e4e2 0000000002625a00
[ 11.635903] 0000000081734200 0000038000913c18 000000008834c6d6 0000038000913ac8
[ 11.635906] Krnl Code:>0000000000000000: 0000 illegal
[ 11.635906] 0000000000000002: 0000 illegal
[ 11.635906] 0000000000000004: 0000 illegal
[ 11.635906] 0000000000000006: 0000 illegal
[ 11.635906] 0000000000000008: 0000 illegal
[ 11.635906] 000000000000000a: 0000 illegal
[ 11.635906] 000000000000000c: 0000 illegal
[ 11.635906] 000000000000000e: 0000 illegal
[ 11.635915] Call Trace:
[ 11.635916] [<0000000000000000>] 0x0
[ 11.635918] [<000000008834e4e2>] ap_queue_init_state+0x82/0xb8
[ 11.635921] [<000000008834ba1c>] ap_scan_domains+0x6fc/0x740
[ 11.635923] [<000000008834c092>] ap_scan_adapter+0x632/0x8b0
[ 11.635925] [<000000008834c3e4>] ap_scan_bus+0xd4/0x288
[ 11.635927] [<00000000879a33ba>] process_one_work+0x19a/0x410
[ 11.635930] Discipline DIAG cannot be used without z/VM
[ 11.635930] [<00000000879a3a2c>] worker_thread+0x3fc/0x560
[ 11.635933] [<00000000879aea60>] kthread+0x120/0x128
[ 11.635936] [<000000008792afa4>] __ret_from_fork+0x3c/0x58
[ 11.635938] [<00000000885ebe62>] ret_from_fork+0xa/0x30
[ 11.635942] Last Breaking-Event-Address:
[ 11.635942] [<000000008834c6d4>] ap_wait+0xcc/0x148
This patch improves the ap_bus_force_rescan() function which is
invoked by the config change callback by checking if a first
initial AP bus scan has been done. If not, the force rescan request
is simple ignored. Anyhow it does not make sense to trigger AP bus
re-scans even before the very first bus scan is complete.
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Holger Dengler <dengler@xxxxxxxxxxxxx>
Signed-off-by: Harald Freudenberger <freude@xxxxxxxxxxxxx>
Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/s390/crypto/ap_bus.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -1030,6 +1030,10 @@ EXPORT_SYMBOL(ap_driver_unregister);
void ap_bus_force_rescan(void)
{
+ /* Only trigger AP bus scans after the initial scan is done */
+ if (atomic64_read(&ap_scan_bus_count) <= 0)
+ return;
+
/* processing a asynchronous bus rescan */
del_timer(&ap_config_timer);
queue_work(system_long_wq, &ap_scan_work);
