5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Vasileios Almpanis <redacted>
commit b15b548d52b43ba8ac4652bc2c7244a8dd1e9622 upstream.
i2c_del_adapter() frees the adapter's debugfs directory before it
unregisters the adapter device, but the new_device sysfs attribute
stays writable until device_del(). A write racing with removal still
reaches i2c_device_probe(), which passes the freed adap->debugfs to
debugfs_create_dir() as the new client's parent:
BUG: KASAN: slab-use-after-free in lookup_noperm_common+0x407/0x430
Read of size 4 at addr ffff88803ef87810 by task syz.0.61/6090
lookup_noperm_common+0x407/0x430
simple_start_creating+0x9c/0x110
debugfs_start_creating+0xdb/0x1a0
debugfs_create_dir+0x24/0x350
i2c_device_probe+0x814/0xbf0
It's technically possible to create a client after i2c_deregister_clients
has run. That client will never be unregistered and make
wait_for_completion hang.
Close the window by removing the new_device attribute at the start of
i2c_del_adapter(). device_remove_file() will drain any clients left.
Fixes: 73febd775bdb ("i2c: create debugfs entry per adapter")
Reported-by: <redacted>
Closes: https://syzkaller.appspot.com/bug?extid=23ad911c819b923238b7
Signed-off-by: Vasileios Almpanis <redacted>
Cc: <redacted> # v6.8+
Tested-by: <redacted>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://patch.msgid.link/20260812-i2c-v2-1-5efaab4c3334@gmail.com (local)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/i2c/i2c-core-base.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1810,6 +1810,12 @@ void i2c_del_adapter(struct i2c_adapter
return;
}
+ /*
+ * This drains any in-flight writers, so all
+ * clients will be caught by i2c_deregister_clients().
+ */
+ device_remove_file(&adap->dev, &dev_attr_new_device);
+
i2c_acpi_remove_space_handler(adap);
i2c_deregister_clients(adap);