Driver core patches for kernel 3.14

PATCH In review Bart Van Assche 2 participants 6 messages Jan 4, 2014 – Jan 8, 2014

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Bart Van Assche

author

2014-01-04 13:19 UTC #0 lore raw

cover Driver core patches for kernel 3.14

This series consists of the following three patches:
0001-kobject-Fix-source-code-comment-spelling.patch 0002-firmware-loader-Add-sparse-annotation.patch 0003-driver-core-Fix-use-after-free-triggered-by-bus_unre.patch

Bart Van Assche

author

2014-01-04 13:20 UTC #1 lore raw

PATCH 1/3 kobject: Fix source code comment spelling

Signed-off-by Bart Van Assche <[email protected]>

---
 lib/kobject.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

lib/kobject.c +1 -1

index 5b4b888..0061f55 100644
@@ -346,7 +346,7 @@ static int kobject_add_varg(struct kobject *kobj, struct kobject *parent,
  *
  * If @parent is set, then the parent of the @kobj will be set to it.
  * If @parent is NULL, then the parent of the @kobj will be set to the
- * kobject associted with the kset assigned to this kobject.  If no kset
+ * kobject associated with the kset assigned to this kobject.  If no kset
  * is assigned to the kobject, then the kobject will be located in the
  * root of the sysfs tree.
  *

Signature · 1 line

1.8.1.4

Bart Van Assche

author

2014-01-04 13:20 UTC #2 lore raw

PATCH 2/3 firmware loader: Add sparse annotation

In reply to Bart Van Assche

Avoid that sparse reports the following warning on __fw_free_buf():

drivers/base/firmware_class.c:230:9: warning: context imbalance in '__fw_free_buf' - unexpected unlock

Signed-off-by Bart Van Assche <[email protected]>

Cc Ming Lei <[email protected]>

---
 drivers/base/firmware_class.c | 1 +
 1 file changed, 1 insertion(+)

drivers/base/firmware_class.c +1 -0

index eb8fb94..c2e4540 100644
@@ -219,6 +219,7 @@ static int fw_lookup_and_allocate_buf(const char *fw_name,
 }
 
 static void __fw_free_buf(struct kref *ref)
+	__releases(&fwc->lock)
 {
 	struct firmware_buf *buf = to_fwbuf(ref);
 	struct firmware_cache *fwc = buf->fwc;

Signature · 1 line

1.8.1.4

Bart Van Assche

author

2014-01-04 13:21 UTC #4 lore raw

PATCH 3/3 driver-core: Fix use-after-free triggered by bus_unregister()

In reply to Bart Van Assche

Avoid that bus_unregister() triggers a use-after-free with CONFIG_DEBUG_KOBJECT_RELEASE=y. This patch avoids that the following sequence triggers a kernel crash with memory poisoning enabled:
* bus_register()
* driver_register()
* driver_unregister()
* bus_unregister()

The above sequence causes the bus private data to be freed from inside the bus_unregister() call although it is not guaranteed in that function that the reference count on the bus private data has dropped to zero. As an example, with CONFIG_DEBUG_KOBJECT_RELEASE=y the ${bus}/drivers kobject is still holding a reference on bus->p->subsys.kobj via its parent pointer at the time the bus private data is freed. Fix this by deferring freeing the bus private data until the last kobject_put() call on bus->p->subsys.kobj.

The kernel oops triggered by the above sequence and with memory poisoning enabled and that is fixed by this patch is as follows:

general protection fault: 0000 [#1] PREEMPT SMP
CPU: 3 PID: 2711 Comm: kworker/3:32 Tainted: G        W  O 3.13.0-rc4-debug+ #1
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Workqueue: events kobject_delayed_cleanup
task: ffff880037f866d0 ti: ffff88003b638000 task.ti: ffff88003b638000
Call Trace:
 [<ffffffff81263105>] ? kobject_get_path+0x25/0x100
 [<ffffffff81264354>] kobject_uevent_env+0x134/0x600
 [<ffffffff8126482b>] kobject_uevent+0xb/0x10
 [<ffffffff81262fa2>] kobject_delayed_cleanup+0xc2/0x1b0
 [<ffffffff8106c047>] process_one_work+0x217/0x700
 [<ffffffff8106bfdb>] ? process_one_work+0x1ab/0x700
 [<ffffffff8106c64b>] worker_thread+0x11b/0x3a0
 [<ffffffff8106c530>] ? process_one_work+0x700/0x700
 [<ffffffff81074b70>] kthread+0xf0/0x110
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
 [<ffffffff815673bc>] ret_from_fork+0x7c/0xb0
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
Code: 89 f8 48 89 e5 f6 82 c0 27 63 81 20 74 15 0f 1f 44 00 00 48 83 c0 01 0f b6 10 f6 82 c0 27 63 81 20 75 f0 5d c3 66 0f 1f 44 00 00 <80> 3f 00 55 48 89 e5 74 15 48 89 f8 0f 1f 40 00 48 83 c0 01 80
RIP  [<ffffffff81267ed0>] strlen+0x0/0x30
 RSP <ffff88003b639c70>
---[ end trace 210f883ef80376aa ]---

Signed-off-by Bart Van Assche <[email protected]>

---
 drivers/base/bus.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

drivers/base/bus.c +11 -2

index 73f6c29..59dc808 100644
@@ -146,8 +146,19 @@ void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
 }
 EXPORT_SYMBOL_GPL(bus_remove_file);
 
+static void bus_release(struct kobject *kobj)
+{
+	struct subsys_private *priv =
+		container_of(kobj, typeof(*priv), subsys.kobj);
+	struct bus_type *bus = priv->bus;
+
+	kfree(priv);
+	bus->p = NULL;
+}
+
 static struct kobj_type bus_ktype = {
 	.sysfs_ops	= &bus_sysfs_ops,
+	.release	= bus_release,
 };
 
 static int bus_uevent_filter(struct kset *kset, struct kobject *kobj)

@@ -953,8 +964,6 @@ void bus_unregister(struct bus_type *bus)
 	kset_unregister(bus->p->devices_kset);
 	bus_remove_file(bus, &bus_attr_uevent);
 	kset_unregister(&bus->p->subsys);
-	kfree(bus->p);
-	bus->p = NULL;
 }
 EXPORT_SYMBOL_GPL(bus_unregister);

Signature · 1 line

1.8.1.4

Ming Lei

Acked-by on v1 2/3

2014-01-08 01:41 UTC #3 lore raw

Re: [PATCH 2/3] firmware loader: Add sparse annotation

In reply to Bart Van Assche

Quoted 6 lines · Bart Van Assche

Avoid that sparse reports the following warning on __fw_free_buf():
drivers/base/firmware_class.c:230:9: warning: context imbalance in '__fw_free_buf' - unexpected unlock
Signed-off-by Bart Van Assche <[email protected]>
Cc Ming Lei <[email protected]>

Bart, thanks.

Acked-by Ming Lei <[email protected]>

Thanks,
--
Ming Lei

Ming Lei

Acked-by on v1 3/3

2014-01-08 02:01 UTC #5 lore raw

Re: [PATCH 3/3] driver-core: Fix use-after-free triggered by bus_unregister()

In reply to Bart Van Assche

Quoted 74 lines · Bart Van Assche

Avoid that bus_unregister() triggers a use-after-free with CONFIG_DEBUG_KOBJECT_RELEASE=y. This patch avoids that the following sequence triggers a kernel crash with memory poisoning enabled:
* bus_register()
* driver_register()
* driver_unregister()
* bus_unregister()
The above sequence causes the bus private data to be freed from inside the bus_unregister() call although it is not guaranteed in that function that the reference count on the bus private data has dropped to zero. As an example, with CONFIG_DEBUG_KOBJECT_RELEASE=y the ${bus}/drivers kobject is still holding a reference on bus->p->subsys.kobj via its parent pointer at the time the bus private data is freed. Fix this by deferring freeing the bus private data until the last kobject_put() call on bus->p->subsys.kobj.
The kernel oops triggered by the above sequence and with memory poisoning enabled and that is fixed by this patch is as follows:
general protection fault: 0000 [#1] PREEMPT SMP
CPU: 3 PID: 2711 Comm: kworker/3:32 Tainted: G        W  O 3.13.0-rc4-debug+ #1
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Workqueue: events kobject_delayed_cleanup
task: ffff880037f866d0 ti: ffff88003b638000 task.ti: ffff88003b638000
Call Trace:
 [<ffffffff81263105>] ? kobject_get_path+0x25/0x100
 [<ffffffff81264354>] kobject_uevent_env+0x134/0x600
 [<ffffffff8126482b>] kobject_uevent+0xb/0x10
 [<ffffffff81262fa2>] kobject_delayed_cleanup+0xc2/0x1b0
 [<ffffffff8106c047>] process_one_work+0x217/0x700
 [<ffffffff8106bfdb>] ? process_one_work+0x1ab/0x700
 [<ffffffff8106c64b>] worker_thread+0x11b/0x3a0
 [<ffffffff8106c530>] ? process_one_work+0x700/0x700
 [<ffffffff81074b70>] kthread+0xf0/0x110
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
 [<ffffffff815673bc>] ret_from_fork+0x7c/0xb0
 [<ffffffff81074a80>] ? insert_kthread_work+0x80/0x80
Code: 89 f8 48 89 e5 f6 82 c0 27 63 81 20 74 15 0f 1f 44 00 00 48 83 c0 01 0f b6 10 f6 82 c0 27 63 81 20 75 f0 5d c3 66 0f 1f 44 00 00 <80> 3f 00 55 48 89 e5 74 15 48 89 f8 0f 1f 40 00 48 83 c0 01 80
RIP  [<ffffffff81267ed0>] strlen+0x0/0x30
 RSP <ffff88003b639c70>
---[ end trace 210f883ef80376aa ]---
Signed-off-by Bart Van Assche <[email protected]>
---
 drivers/base/bus.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)
drivers/base/bus.c +11 -0
index 73f6c29..59dc808 100644
@@ -146,8 +146,19 @@ void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
 }
 EXPORT_SYMBOL_GPL(bus_remove_file);
 
+static void bus_release(struct kobject *kobj)
+{
+       struct subsys_private *priv =
+               container_of(kobj, typeof(*priv), subsys.kobj);
+       struct bus_type *bus = priv->bus;
+
+       kfree(priv);
+       bus->p = NULL;
+}
+
 static struct kobj_type bus_ktype = {
        .sysfs_ops      = &bus_sysfs_ops,
+       .release        = bus_release,
 };
 
 static int bus_uevent_filter(struct kset *kset, struct kobject *kobj)

drivers/base/bus.c void bus_unregister(struct bus_type *bus) · line 968

Quoted 7 lines

drivers/base/bus.c +0 -2

@@ -953,8 +964,6 @@ void bus_unregister(struct bus_type *bus)
        kset_unregister(bus->p->devices_kset);
        bus_remove_file(bus, &bus_attr_uevent);
        kset_unregister(&bus->p->subsys);
-       kfree(bus->p);
-       bus->p = NULL;
 }
 EXPORT_SYMBOL_GPL(bus_unregister);

Looks the fix is fine,

Acked-by Ming Lei <[email protected]>

Thanks,
--
Ming Lei