[PATCH 5.4 345/367] kobject: Add sanity check for kset->kobj.ktype in kset_register()

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5.4-stable review patch.  If anyone has any objections, please let me know.


From: Zhen Lei <thunder.leizhen@xxxxxxxxxx>

[ Upstream commit 4d0fe8c52bb3029d83e323c961221156ab98680b ]

When I register a kset in the following way:
	static struct kset my_kset;
	kobject_set_name(&my_kset.kobj, "my_kset");
        ret = kset_register(&my_kset);

A null pointer dereference exception is occurred:
[ 4453.568337] Unable to handle kernel NULL pointer dereference at \
virtual address 0000000000000028
... ...
[ 4453.810361] Call trace:
[ 4453.813062]  kobject_get_ownership+0xc/0x34
[ 4453.817493]  kobject_add_internal+0x98/0x274
[ 4453.822005]  kset_register+0x5c/0xb4
[ 4453.825820]  my_kobj_init+0x44/0x1000 [my_kset]
... ...

Because I didn't initialize my_kset.kobj.ktype.

According to the description in Documentation/core-api/kobject.rst:
 - A ktype is the type of object that embeds a kobject.  Every structure
   that embeds a kobject needs a corresponding ktype.

So add sanity check to make sure kset->kobj.ktype is not NULL.

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230805084114.1298-2-thunder.leizhen@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
 lib/kobject.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/kobject.c b/lib/kobject.c
index 0c6d17503a113..c4025a880d753 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -877,6 +877,11 @@ int kset_register(struct kset *k)
 	if (!k)
 		return -EINVAL;
+	if (!k->kobj.ktype) {
+		pr_err("must have a ktype to be initialized properly!\n");
+		return -EINVAL;
+	}
 	err = kobject_add_internal(&k->kobj);
 	if (err)

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