Mark Lord wrote:
Mark Lord wrote:
Mark Lord wrote:
...
And here is a "prevented" oops, courtesy of the patch (2.6.23.8).
These are easy to reproduce (just jiggle the connection on an
attached USB multi-card reader with a CF card inserted):
...
[ 347.099562] usb 5-6: USB disconnect, address 10
[ 347.101077] BUG: unable to handle kernel NULL pointer dereference
at virtual address 00000000
...
Mmmm.. that's odd. It *did* Oops there. I wonder how/why ?
...
Ahh.. it was the *other* call to strlen() that was crapping out.
Here's an updated patch to prevent the Oops:
* * * *
While doing insert/remove (quickly) tests on USB,
I managed to trigger an Oops on 2.6.23.8 on a call
to strlen() in make_class_name().
USB maintainers can try this themselves, by plugging in an
external USB XX-in-1 flash reader, with a CF card inserted.
Then just jiggle the connection so that the device connects
and disconnects rapidly. This may not sound realistic,
but there's definitely a race in there, and this is a quick
way to reproduce it if need be.
The patch below prevents the oops, but still keeps the bug visible.
Signed-off-by: Mark Lord <[email protected]>
---
Patch applies to both 2.6.24 and 2.6.23.
--- old/drivers/base/class.c 2007-11-29 10:51:43.000000000 -0500
+++ linux/drivers/base/class.c 2007-11-29 13:00:15.000000000 -0500
@@ -352,9 +352,22 @@
char *make_class_name(const char *name, struct kobject *kobj)
{
char *class_name;
+ const char *kname;
int size;
- size = strlen(name) + strlen(kobject_name(kobj)) + 2;
+ /* Rapidly inserting/removing a USB device (others?)
+ * can trigger an Oops on the strlen() call.
+ * Cause unknown yet, so prevent the Oops
+ * but don't mask the issue.
+ */
+ kname = kobject_name(kobj);
+ if (!kname || !name) {
+ printk(KERN_ERR "make_class_name: name=%p kname=%p\n",
+ name, kname);
+ BUG_ON(1);
+ return NULL;
+ }
+ size = strlen(name) + strlen(kname) + 2;
class_name = kmalloc(size, GFP_KERNEL);
if (!class_name)
-
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