On Wed, 14 Nov 2018, David Herrmann wrote: > This reverts commit 336fd4f5f25157e9e8bd50e898a1bbcd99eaea46. > > 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@xxxxxxxxx> > --- > drivers/hid/uhid.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c > index fefedc0b4dc6..0dfdd0ac7120 100644 > --- a/drivers/hid/uhid.c > +++ b/drivers/hid/uhid.c > @@ -496,12 +496,13 @@ 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); Applied, thanks. -- Jiri Kosina SUSE Labs
