linux-kernel - Re: [PATCH] tty: vt: keyboard: Fix uninitialized variables in vt_do_kdgkb

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Message-ID: <2025041107-postbox-bonanza-2049@gregkh>
Date: Fri, 11 Apr 2025 13:28:01 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Purva Yeshi <purvayeshi550@...il.com>
Cc: jirislaby@...nel.org, tglx@...utronix.de, hdegoede@...hat.com,
	mingo@...nel.org, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty: vt: keyboard: Fix uninitialized variables in
 vt_do_kdgkb_ioctl

On Fri, Apr 11, 2025 at 04:45:48PM +0530, Purva Yeshi wrote:
> Fix Smatch-detected issue:
> 
> drivers/tty/vt/keyboard.c:2106 vt_do_kdgkb_ioctl() error:
> uninitialized symbol 'kbs'.
> drivers/tty/vt/keyboard.c:2108 vt_do_kdgkb_ioctl() error:
> uninitialized symbol 'ret'.
> 
> Fix uninitialized variable warnings reported by Smatch in
> vt_do_kdgkb_ioctl(). The variables kbs and ret were used in the kfree
> and return statements without guaranteed initialization paths, leading to
> potential undefined behavior or false positives during static analysis.
> 
> Initialize char *kbs to NULL and int ret to -EINVAL at declaration.
> This ensures safe use of kfree(kbs) and return ret regardless of control
> flow. Also add a default case in the switch to preserve fallback behavior.

When you say "also" in a patch, that is a HUGE flag that this should be
split up into a separate change.  Please do that here, don't mix changes
that have nothing to do with each other together into one.

Also, why isn't the compilers noticing that these are uninitialized
variables?  Are you sure the warning is correct?

thanks,

greg k-h