Re: [PATCH v4 3/7] s390: zcrypt: driver callback to indicate resource in use

Harald Freudenberger
2019-06-17T09:29:07Z

On 13.06.19 21:39, Tony Krowiak wrote:
> Introduces a new driver callback to prevent a root user from unbinding
> an AP queue from its device driver if the queue is in use. This prevents
> a root user from inadvertently taking a queue away from a guest and
> giving it to the host, or vice versa. The callback will be invoked
> whenever a change to the AP bus's apmask or aqmask sysfs interfaces may
> result in one or more AP queues being removed from its driver. If the
> callback responds in the affirmative for any driver queried, the change
> to the apmask or aqmask will be rejected with a device in use error.
>
> For this patch, only non-default drivers will be queried. Currently,
> there is only one non-default driver, the vfio_ap device driver. The
> vfio_ap device driver manages AP queues passed through to one or more
> guests and we don't want to unexpectedly take AP resources away from
> guests which are most likely independently administered.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
> drivers/s390/crypto/ap_bus.c | 138 +++++++++++++++++++++++++++++++++++++++++--
> drivers/s390/crypto/ap_bus.h | 3 +
> 2 files changed, 135 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
> index b9fc502c58c2..1b06f47d0d1c 100644
> --- a/drivers/s390/crypto/ap_bus.c
> +++ b/drivers/s390/crypto/ap_bus.c
> @@ -35,6 +35,7 @@
> #include <linux/mod_devicetable.h>
> #include <linux/debugfs.h>
> #include <linux/ctype.h>
> +#include <linux/module.h>
>
> #include "ap_bus.h"
> #include "ap_debug.h"
> @@ -998,9 +999,11 @@ int ap_parse_mask_str(const char *str,
> newmap = kmalloc(size, GFP_KERNEL);
> if (!newmap)
> return -ENOMEM;
> - if (mutex_lock_interruptible(lock)) {
> - kfree(newmap);
> - return -ERESTARTSYS;
> + if (lock) {
> + if (mutex_lock_interruptible(lock)) {
> + kfree(newmap);
> + return -ERESTARTSYS;
> + }
> }
>
> if (*str == '+' || *str == '-') {
> @@ -1012,7 +1015,10 @@ int ap_parse_mask_str(const char *str,
> }
> if (rc == 0)
> memcpy(bitmap, newmap, size);
> - mutex_unlock(lock);
> +
> + if (lock)
> + mutex_unlock(lock);
> +
> kfree(newmap);
> return rc;
> }
> @@ -1199,12 +1205,72 @@ static ssize_t apmask_show(struct bus_type *bus, char *buf)
> return rc;
> }
>
> +int __verify_card_reservations(struct device_driver *drv, void *data)
> +{
> + int rc = 0;
> + struct ap_driver *ap_drv = to_ap_drv(drv);
> + unsigned long *newapm = (unsigned long *)data;
> +
> + /*
> + * If the reserved bits do not identify cards reserved for use by the
> + * non-default driver, there is no need to verify the driver is using
> + * the queues.
> + */
> + if (ap_drv->flags & AP_DRIVER_FLAG_DEFAULT)
> + return 0;
> +
> + /* The non-default driver's module must be loaded */
> + if (!try_module_get(drv->owner))
> + return 0;
> +
> + if (ap_drv->in_use)
> + if (ap_drv->in_use(newapm, ap_perms.aqm))
> + rc = -EADDRINUSE;
> +
> + module_put(drv->owner);
> +
> + return rc;
> +}
> +
> +static int apmask_commit(unsigned long *newapm)
> +{
> + int rc;
> + unsigned long reserved[BITS_TO_LONGS(AP_DEVICES)];
> +
> + /*
> + * Check if any bits in the apmask have been set which will
> + * result in queues being removed from non-default drivers
> + */
> + if (bitmap_andnot(reserved, newapm, ap_perms.apm, AP_DEVICES)) {
> + rc = (bus_for_each_drv(&ap_bus_type, NULL, reserved,
> + __verify_card_reservations));
Why surround the bus_for_each_drv() with additional parenthesis ?
> + if (rc)
> + return rc;
> + }
> +
> + memcpy(ap_perms.apm, newapm, APMASKSIZE);
> +
> + return 0;
> +}
> +
> static ssize_t apmask_store(struct bus_type *bus, const char *buf,
> size_t count)
> {
> int rc;
> + unsigned long newapm[BITS_TO_LONGS(AP_DEVICES)];
> +
> + memcpy(newapm, ap_perms.apm, APMASKSIZE);
> +
> + rc = ap_parse_mask_str(buf, newapm, AP_DEVICES, NULL);
> + if (rc)
> + return rc;
> +
> + if (mutex_lock_interruptible(&ap_perms_mutex))
> + return -ERESTARTSYS;
This lock is too late. Move it before the memcpy(newapm, ap_perms.apm, APMASKSIZE);
> +
> + rc = apmask_commit(newapm);
> + mutex_unlock(&ap_perms_mutex);
>
> - rc = ap_parse_mask_str(buf, ap_perms.apm, AP_DEVICES, &ap_perms_mutex);
> if (rc)
> return rc;
>
> @@ -1230,12 +1296,72 @@ static ssize_t aqmask_show(struct bus_type *bus, char *buf)
> return rc;
> }
>
> +int __verify_queue_reservations(struct device_driver *drv, void *data)
> +{
> + int rc = 0;
> + struct ap_driver *ap_drv = to_ap_drv(drv);
> + unsigned long *newaqm = (unsigned long *)data;
> +
> + /*
> + * If the reserved bits do not identify queues reserved for use by the
> + * non-default driver, there is no need to verify the driver is using
> + * the queues.
> + */
> + if (ap_drv->flags & AP_DRIVER_FLAG_DEFAULT)
> + return 0;
> +
> + /* The non-default driver's module must be loaded */
> + if (!try_module_get(drv->owner))
> + return 0;
> +
> + if (ap_drv->in_use)
> + if (ap_drv->in_use(ap_perms.apm, newaqm))
> + rc = -EADDRINUSE;
> +
> + module_put(drv->owner);
> +
> + return rc;
> +}
> +
> +static int aqmask_commit(unsigned long *newaqm)
> +{
> + int rc;
> + unsigned long reserved[BITS_TO_LONGS(AP_DOMAINS)];
> +
> + /*
> + * Check if any bits in the aqmask have been set which will
> + * result in queues being removed from non-default drivers
> + */
> + if (bitmap_andnot(reserved, newaqm, ap_perms.aqm, AP_DOMAINS)) {
> + rc = (bus_for_each_drv(&ap_bus_type, NULL, reserved,
> + __verify_queue_reservations));
Same here: please remove the surrounding ( ... ).
> + if (rc)
> + return rc;
> + }
> +
> + memcpy(ap_perms.aqm, newaqm, APMASKSIZE);
APMASKSIZE -> AQMASKSIZE
> +
> + return 0;
> +}
> +
> static ssize_t aqmask_store(struct bus_type *bus, const char *buf,
> size_t count)
> {
> int rc;
> + unsigned long newaqm[BITS_TO_LONGS(AP_DEVICES)];
> +
> + memcpy(newaqm, ap_perms.aqm, AQMASKSIZE);
> +
> + rc = ap_parse_mask_str(buf, newaqm, AP_DOMAINS, NULL);
> + if (rc)
> + return rc;
> +
> + if (mutex_lock_interruptible(&ap_perms_mutex))
> + return -ERESTARTSYS;
Please move the lock before the memcpy(newaqm, ...)
> +
> + rc = aqmask_commit(newaqm);
> + mutex_unlock(&ap_perms_mutex);
>
> - rc = ap_parse_mask_str(buf, ap_perms.aqm, AP_DOMAINS, &ap_perms_mutex);
> if (rc)
> return rc;
>
> diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
> index 6f3cf37776ca..0f865c5545f2 100644
> --- a/drivers/s390/crypto/ap_bus.h
> +++ b/drivers/s390/crypto/ap_bus.h
> @@ -137,6 +137,7 @@ struct ap_driver {
> void (*remove)(struct ap_device *);
> void (*suspend)(struct ap_device *);
> void (*resume)(struct ap_device *);
> + bool (*in_use)(unsigned long *apm, unsigned long *aqm);
> };
>
> #define to_ap_drv(x) container_of((x), struct ap_driver, driver)
> @@ -265,6 +266,8 @@ void ap_queue_reinit_state(struct ap_queue *aq);
> struct ap_card *ap_card_create(int id, int queue_depth, int raw_device_type,
> int comp_device_type, unsigned int functions);
>
> +#define APMASKSIZE (BITS_TO_LONGS(AP_DEVICES) * sizeof(unsigned long))
> +#define AQMASKSIZE (BITS_TO_LONGS(AP_DOMAINS) * sizeof(unsigned long))
add one empty line here please
> struct ap_perms {
> unsigned long ioctlm[BITS_TO_LONGS(AP_IOCTLS)];
> unsigned long apm[BITS_TO_LONGS(AP_DEVICES)];