From: Dirk Behme <dirk.behme@de.bosch.com>
To: <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <dirk.behme@de.bosch.com>, Rafael J Wysocki <rafael@kernel.org>,
<syzbot+ffa8143439596313a85a@syzkaller.appspotmail.com>,
Eugeniu Rosca <eugeniu.rosca@bosch.com>
Subject: [PATCH] drivers: core: Make dev->driver usage safe in dev_uevent()
Date: Tue, 30 Apr 2024 06:55:31 +0200 [thread overview]
Message-ID: <20240430045531.4062232-1-dirk.behme@de.bosch.com> (raw)
Inspired by the function dev_driver_string() in the same file make sure
in case of uninitialization dev->driver is used safely in dev_uevent(),
as well.
This change is based on the observation of the following race condition:
Thread #1:
==========
really_probe() {
...
probe_failed:
...
device_unbind_cleanup(dev) {
...
dev->driver = NULL; // <= Failed probe sets dev->driver to NULL
...
}
...
}
Thread #2:
==========
dev_uevent() {
...
if (dev->driver)
// If dev->driver is NULLed from really_probe() from here on,
// after above check, the system crashes
add_uevent_var(env, "DRIVER=%s", dev->driver->name);
dev_driver_string() can't be used here because we want NULL and not
anything else in the non-init case.
Similar cases are reported by syzkaller in
https://syzkaller.appspot.com/bug?extid=ffa8143439596313a85a
But these are regarding the *initialization* of dev->driver
dev->driver = drv;
As this switches dev->driver to non-NULL these reports can be considered
to be false-positives (which should be "fixed" by this commit, as well,
though).
Fixes: 239378f16aa1 ("Driver core: add uevent vars for devices of a class")
Cc: syzbot+ffa8143439596313a85a@syzkaller.appspotmail.com
Reviewed-by: Eugeniu Rosca <eugeniu.rosca@bosch.com>
Tested-by: Eugeniu Rosca <eugeniu.rosca@bosch.com>
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
---
drivers/base/core.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5f4e03336e68..99ead727c08f 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2639,6 +2639,7 @@ static const char *dev_uevent_name(const struct kobject *kobj)
static int dev_uevent(const struct kobject *kobj, struct kobj_uevent_env *env)
{
const struct device *dev = kobj_to_dev(kobj);
+ struct device_driver *drv;
int retval = 0;
/* add device node properties if present */
@@ -2667,8 +2668,12 @@ static int dev_uevent(const struct kobject *kobj, struct kobj_uevent_env *env)
if (dev->type && dev->type->name)
add_uevent_var(env, "DEVTYPE=%s", dev->type->name);
- if (dev->driver)
- add_uevent_var(env, "DRIVER=%s", dev->driver->name);
+ /* dev->driver can change to NULL underneath us because of unbinding
+ * or failing probe(), so be careful about accessing it.
+ */
+ drv = READ_ONCE(dev->driver);
+ if (drv)
+ add_uevent_var(env, "DRIVER=%s", drv->name);
/* Add common DT information about the device */
of_device_uevent(dev, env);
--
2.28.0
next reply other threads:[~2024-04-30 4:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 4:55 Dirk Behme [this message]
2024-04-30 7:20 ` [PATCH] drivers: core: Make dev->driver usage safe in dev_uevent() Greg Kroah-Hartman
2024-04-30 8:17 ` Eugeniu Rosca
2024-04-30 8:27 ` Greg Kroah-Hartman
2024-04-30 13:18 ` Eugeniu Rosca
2024-04-30 8:23 ` Dirk Behme
2024-04-30 8:41 ` Greg Kroah-Hartman
2024-04-30 8:50 ` Dirk Behme
2024-04-30 8:57 ` Greg Kroah-Hartman
2024-05-06 6:04 ` Dirk Behme
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