Commit 4d26d1d1 authored Nov 14, 2018 by David Herrmann Committed by Jiri Kosina Nov 19, 2018

Revert "HID: uhid: use strlcpy() instead of strncpy()"



This reverts commit 336fd4f5.

Please note that `strlcpy()` does *NOT* do what you think it does.
strlcpy() *ALWAYS* reads the full input string, regardless of the
'length' parameter. That is, if the input is not zero-terminated,
strlcpy() will *READ* beyond input boundaries. It does this, because it
always returns the size it *would* copy if the target was big enough,
not the truncated size it actually copied.

The original code was perfectly fine. The hid device is
zero-initialized and the strncpy() functions copied up to n-1
characters. The result is always zero-terminated this way.

This is the third time someone tried to replace strncpy with strlcpy in
this function, and gets it wrong. I now added a comment that should at
least make people reconsider.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

parent 8c01db76

drivers/hid/uhid.c

+7 −6

Original line number	Diff line number	Diff line
		@@ -497,12 +497,13 @@ static int uhid_dev_create2(struct uhid_device *uhid,
		goto err_free;
		}

		len = min(sizeof(hid->name), sizeof(ev->u.create2.name));
		strlcpy(hid->name, ev->u.create2.name, len);
		len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys));
		strlcpy(hid->phys, ev->u.create2.phys, len);
		len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq));
		strlcpy(hid->uniq, ev->u.create2.uniq, len);
		/* @hid is zero-initialized, strncpy() is correct, strlcpy() not */
		len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1;
		strncpy(hid->name, ev->u.create2.name, len);
		len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1;
		strncpy(hid->phys, ev->u.create2.phys, len);
		len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1;
		strncpy(hid->uniq, ev->u.create2.uniq, len);

		hid->ll_driver = &uhid_hid_driver;
		hid->bus = ev->u.create2.bus;

Admin message