Commit e387753c authored by Sascha Silbe's avatar Sascha Silbe Committed by Martin Schwidefsky

s390/zcrypt: Fix kernel crash on systems without AP bus support

On systems without AP bus (e.g. KVM) the kernel crashes during init
calls when zcrypt is built-in:

kernel BUG at drivers/base/driver.c:153!
illegal operation: 0001 ilc:1 [#1] SMP
Modules linked in:
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.2.0+ #221
task: 0000000010a40000 ti: 0000000010a48000 task.ti:0000000010a48000
Krnl PSW : 0704c00180000000 0000000000592bd6(driver_register+0x106/0x140)
           R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 EA:3
           0000000000000012 0000000000000000 0000000000c45328 0000000000c44e30
           00000000009ef63c 000000000067f598 0000000000cf3c58 0000000000000000
           000000000000007b 0000000000cb1030 0000000000000002 0000000000000000
           0000000000ca8580 0000000010306700 00000000001001d8 0000000010a4bd88
Krnl Code: 0000000000592bc6: f0b00004ebcf	srp 4(12,%r0),3023(%r14),0
           0000000000592bcc: f0a0000407f4       srp     4(11,%r0),2036,0
          #0000000000592bd2: a7f40001           brc     15,592bd4
          >0000000000592bd6: e330d0000004       lg      %r3,0(%r13)
           0000000000592bdc: c0200021edfd       larl    %r2,9d07d6
           0000000000592be2: c0e500126d8f       brasl   %r14,7e0700
           0000000000592be8: e330d0080004       lg      %r3,8(%r13)
           0000000000592bee: a7f4ffab           brc     15,592b44
Call Trace:
([<00000000001001c8>] do_one_initcall+0x90/0x1d0)
 [<0000000000c6dd34>] kernel_init_freeable+0x1e4/0x2a0
 [<00000000007db53a>] kernel_init+0x2a/0x120
 [<00000000007e8ece>] kernel_thread_starter+0x6/0xc
 [<00000000007e8ec8>] kernel_thread_starter+0x0/0xc
Last Breaking-Event-Address:
 [<0000000000592bd2>] driver_register+0x102/0x140

When zcrypt is built as a module, the module loader ensures that the
driver modules cannot be loaded if the AP bus module returns an error
during initialisation. But if zcrypt and the driver are built-in, the
driver is getting initialised even if the AP bus initialisation
failed. The driver invokes ap_driver_register() during initialisation,
which then causes operations on uninitialised data structures to be
performed.

Explicitly protect ap_driver_register() by introducing an
"initialised" flag that gets set iff the AP bus initialisation was
successful. When the AP bus initialisation failed,
ap_driver_register() will error out with -ENODEV, causing the driver
initialisation to fail as well.

Test results:
1. Inside KVM (no AP bus), zcrypt built-in

   Boots. /sys/bus/ap not present (expected).

2. Inside KVM (no AP bus), zcrypt as module

   Boots. Loading zcrypt_cex4 fails because loading ap_bus fails
   (expected).

3. On LPAR with CEX5, zcrypt built-in

   Boots. /sys/bus/ap/devices/card* present but .../card*/type missing
   (i.e. zcrypt_device_register() fails, unrelated issue).

4. On LPAR with CEX5, zcrypt as module

   Boots. Loading zcrypt_cex4 successful,
   /sys/bus/ap/devices/card*/type present. No further testing
   (user-space functionality) was done.
Signed-off-by: default avatarSascha Silbe <silbe@linux.vnet.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 18e22a17
...@@ -74,6 +74,7 @@ static struct device *ap_root_device = NULL; ...@@ -74,6 +74,7 @@ static struct device *ap_root_device = NULL;
static struct ap_config_info *ap_configuration; static struct ap_config_info *ap_configuration;
static DEFINE_SPINLOCK(ap_device_list_lock); static DEFINE_SPINLOCK(ap_device_list_lock);
static LIST_HEAD(ap_device_list); static LIST_HEAD(ap_device_list);
static bool initialised;
/* /*
* Workqueue timer for bus rescan. * Workqueue timer for bus rescan.
...@@ -1384,6 +1385,9 @@ int ap_driver_register(struct ap_driver *ap_drv, struct module *owner, ...@@ -1384,6 +1385,9 @@ int ap_driver_register(struct ap_driver *ap_drv, struct module *owner,
{ {
struct device_driver *drv = &ap_drv->driver; struct device_driver *drv = &ap_drv->driver;
if (!initialised)
return -ENODEV;
drv->bus = &ap_bus_type; drv->bus = &ap_bus_type;
drv->probe = ap_device_probe; drv->probe = ap_device_probe;
drv->remove = ap_device_remove; drv->remove = ap_device_remove;
...@@ -1808,6 +1812,7 @@ int __init ap_module_init(void) ...@@ -1808,6 +1812,7 @@ int __init ap_module_init(void)
goto out_pm; goto out_pm;
queue_work(system_long_wq, &ap_scan_work); queue_work(system_long_wq, &ap_scan_work);
initialised = true;
return 0; return 0;
...@@ -1837,6 +1842,7 @@ void ap_module_exit(void) ...@@ -1837,6 +1842,7 @@ void ap_module_exit(void)
{ {
int i; int i;
initialised = false;
ap_reset_domain(); ap_reset_domain();
ap_poll_thread_stop(); ap_poll_thread_stop();
del_timer_sync(&ap_config_timer); del_timer_sync(&ap_config_timer);
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment