On 2022/10/24 22:53, Greg KH wrote:
On Mon, Oct 24, 2022 at 10:39:44PM +0800, Yang Yingliang wrote:
On 2022/10/24 21:52, Greg KH wrote:
On Mon, Oct 24, 2022 at 08:19:10PM +0800, Yang Yingliang wrote:
Inject fault while loading module, kset_register() may fail.
If it fails, the name allocated by kobject_set_name() which
is called before kset_register() is leaked, because refcount
of kobject is hold in kset_init().
As a kset may be embedded in a larger structure which needs
be freed in release() function or error path in callers, we
can not call kset_put() in kset_register(), or it will cause
double free, so just call kfree_const() to free the name and
set it to NULL.
With this fix, the callers don't need to care about the name
freeing and call an extra kset_put() if kset_register() fails.
Suggested-by: Luben Tuikov <luben.tuikov@xxxxxxx>
Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
---
v1 -> v2:
Free name inside of kset_register() instead of calling kset_put()
in drivers.
---
lib/kobject.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/lib/kobject.c b/lib/kobject.c
index a0b2dbfcfa23..3409a89c81e5 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -834,6 +834,9 @@ EXPORT_SYMBOL_GPL(kobj_sysfs_ops);
/**
* kset_register() - Initialize and add a kset.
* @k: kset.
+ *
+ * NOTE: On error, the kset.kobj.name allocated by() kobj_set_name()
+ * which is called before kset_register() in caller need be freed.
This comment doesn't make any sense anymore. No caller needs to worry
about this, right?
With this fix, the name is freed inside of kset_register(), it can not be
accessed,
Agreed.
if it allocated dynamically, but callers don't know this if no comment here,
they may use it in error path (something like to print error message with
it),
so how about comment like this to tell callers not to use the name:
NOTE: On error, the kset.kobj.name allocated by() kobj_set_name()
is freed, it can not be used any more.
Sure, that's a better way to word it.
*/
int kset_register(struct kset *k)
{
@@ -844,8 +847,11 @@ int kset_register(struct kset *k)
kset_init(k);
err = kobject_add_internal(&k->kobj);
- if (err)
+ if (err) {
+ kfree_const(k->kobj.name);
+ k->kobj.name = NULL;
Why are you setting the name here to NULL?
I set it to NULL to avoid accessing bad pointer in callers,
if callers use it in error path, current callers won't use this
name pointer in error path, so we can remove this assignment?
Ah, I didn't think about using it on error paths. Ideally that would
never happen, but that's good to set just to make it obvious. How about
adding a small comment here saying why you are setting it so we all
remember it in 5 years when we look at the code again.
OK, I can add it in v3.
Thanks,
Yang
thanks,
greg k-h
.
