From: Lizhi Xu Date: Mon, 14 Apr 2025 07:11:23 +0000 (+0800) Subject: software node: Prevent link creation failure from causing kobj reference count imbalance X-Git-Tag: v6.15-rc4~24^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bc2c46426f2d95e58c82f394531afdd034c8706c;p=thirdparty%2Fkernel%2Flinux.git software node: Prevent link creation failure from causing kobj reference count imbalance syzbot reported a uaf in software_node_notify_remove. [1] When any of the two sysfs_create_link() in software_node_notify() fails, the swnode->kobj reference count will not increase normally, which will cause swnode to be released incorrectly due to the imbalance of kobj reference count when executing software_node_notify_remove(). Increase the reference count of kobj before creating the link to avoid uaf. [1] BUG: KASAN: slab-use-after-free in software_node_notify_remove+0x1bc/0x1c0 drivers/base/swnode.c:1108 Read of size 1 at addr ffff888033c08908 by task syz-executor105/5844 Freed by task 5844: software_node_notify_remove+0x159/0x1c0 drivers/base/swnode.c:1106 device_platform_notify_remove drivers/base/core.c:2387 [inline] Fixes: 9eb59204d519 ("iommufd/selftest: Add set_dev_pasid in mock iommu") Reported-by: syzbot+2ff22910687ee0dfd48e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2ff22910687ee0dfd48e Tested-by: syzbot+2ff22910687ee0dfd48e@syzkaller.appspotmail.com Signed-off-by: Lizhi Xu Reviewed-by: Sakari Ailus Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/20250414071123.1228331-1-lizhi.xu@windriver.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c index b1726a3515f6f..5c78fa6ae7725 100644 --- a/drivers/base/swnode.c +++ b/drivers/base/swnode.c @@ -1080,6 +1080,7 @@ void software_node_notify(struct device *dev) if (!swnode) return; + kobject_get(&swnode->kobj); ret = sysfs_create_link(&dev->kobj, &swnode->kobj, "software_node"); if (ret) return; @@ -1089,8 +1090,6 @@ void software_node_notify(struct device *dev) sysfs_remove_link(&dev->kobj, "software_node"); return; } - - kobject_get(&swnode->kobj); } void software_node_notify_remove(struct device *dev)