From: Pavel Skripkin > Sent: 06 November 2021 11:24 > > Hi, Ajay! > > On 11/6/21 12:20, Ajay Garg wrote: > > Both (statically-allocated) "user_kdgkb->kb_string" and > > (dynamically-allocated) "kbs" are of length "len", so we must > > not copy more than "len" bytes. > > > > Signed-off-by: Ajay Garg <ajaygargnsit@xxxxxxxxx> > > --- > > drivers/tty/vt/keyboard.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c > > index c7fbbcdcc346..dfef7de8a057 100644 > > --- a/drivers/tty/vt/keyboard.c > > +++ b/drivers/tty/vt/keyboard.c > > @@ -2070,7 +2070,7 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) > > len = strlcpy(kbs, func_table[kb_func] ? : "", len); > > ^^^^^^^^^ > > len is reinitialized here, i.e len passed to kmalloc and len passed to > copy_to_user() can be different. > > strlcpy() returns strlen() of source string (2nd argument), that's why > we need +1 here to pass null byte to user. > > Am I missing something? You want strscpy() - returns the number of characters/bytes it copied. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
