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s390/cio: use generic driver_override infrastructure

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When a driver is probed through __driver_attach(), the bus' match()
callback is called without the device lock held, thus accessing the
driver_override field without a lock, which can cause a UAF.

Fix this by using the driver-core driver_override infrastructure taking
care of proper locking internally.

Note that calling match() from __driver_attach() without the device lock
held is intentional. [1]

Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
Reported-by: Gui-Dong Han <hanguidong02@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789
Fixes: ebc3d17915 ("s390/cio: introduce driver_override on the css bus")
Reviewed-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Link: https://patch.msgid.link/20260324005919.2408620-10-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Danilo Krummrich
2026-03-24 01:59:13 +01:00
parent 85bb534ff1
commit ac4d8bb6e2
2 changed files with 4 additions and 35 deletions
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34
drivers/s390/cio/css.c
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@@ -159,7 +159,6 @@ static void css_subchannel_release(struct device *dev)
sch->config.intparm = 0;
cio_commit_config(sch);
kfree(sch->driver_override);
kfree(sch);
}
@@ -323,37 +322,9 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
static DEVICE_ATTR_RO(modalias);
static ssize_t driver_override_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct subchannel *sch = to_subchannel(dev);
int ret;
ret = driver_set_override(dev, &sch->driver_override, buf, count);
if (ret)
return ret;
return count;
}
static ssize_t driver_override_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct subchannel *sch = to_subchannel(dev);
ssize_t len;
device_lock(dev);
len = sysfs_emit(buf, "%s\n", sch->driver_override);
device_unlock(dev);
return len;
}
static DEVICE_ATTR_RW(driver_override);
static struct attribute *subch_attrs[] = {
&dev_attr_type.attr,
&dev_attr_modalias.attr,
&dev_attr_driver_override.attr,
NULL,
};
@@ -1356,9 +1327,11 @@ static int css_bus_match(struct device *dev, const struct device_driver *drv)
struct subchannel *sch = to_subchannel(dev);
const struct css_driver *driver = to_cssdriver(drv);
struct css_device_id *id;
int ret;
/* When driver_override is set, only bind to the matching driver */
if (sch->driver_override && strcmp(sch->driver_override, drv->name))
ret = device_match_driver_override(dev, drv);
if (ret == 0)
return 0;
for (id = driver->subchannel_type; id->match_flags; id++) {
@@ -1415,6 +1388,7 @@ static int css_uevent(const struct device *dev, struct kobj_uevent_env *env)
static const struct bus_type css_bus_type = {
.name = "css",
.driver_override = true,
.match = css_bus_match,
.probe = css_probe,
.remove = css_remove,