Commit 95e8e7ee authored by Azeem Shaikh's avatar Azeem Shaikh Committed by Greg Kroah-Hartman
Browse files

vt: Replace strlcpy with strscpy 

strlcpy() reads the entire source buffer first and returns the size of
the source string, not the destination string, which can be accidentally
misused [1].

The copy_to_user() call uses @len returned from strlcpy() directly
without checking its value. This could potentially lead to read
overflow. There is no existing bug since @len is always guaranteed to be
greater than hardcoded strings in @func_table[kb_func]. But as written
it is very fragile and specifically uses a strlcpy() result without sanity
checking and using it to copy to userspace.

In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89



Signed-off-by: default avatarAzeem Shaikh <azeems@google.com>
Reviewed-by: default avatarJustin Stitt <justinstitt@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230919192156.121503-1-azeems@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 29bff582

drivers/tty/vt/keyboard.c

+5 −2
Original line number Diff line number Diff line
@@ -2079,12 +2079,15 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) 
			return -ENOMEM;



		spin_lock_irqsave(&func_buf_lock, flags);

		len = strlcpy(kbs, func_table[kb_func] ? : "", len);

		len = strscpy(kbs, func_table[kb_func] ? : "", len);

		spin_unlock_irqrestore(&func_buf_lock, flags);



		if (len < 0) {

			ret = -ENOSPC;

			break;

		}

		ret = copy_to_user(user_kdgkb->kb_string, kbs, len + 1) ?

			-EFAULT : 0;



		break;

	}

	case KDSKBSENT: