linux-kernel - Re: [PATCH] tty: serial: 8250: Fix uninitialized variable warnings in pci_oxsemi_tornado_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <2025041110-simmering-bogus-7a1d@gregkh>
Date: Fri, 11 Apr 2025 14:29:27 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Purva Yeshi <purvayeshi550@...il.com>
Cc: jirislaby@...nel.org, andriy.shevchenko@...ux.intel.com,
	arnd@...nel.org, cang1@...e.co.uk, bhelgaas@...gle.com,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty: serial: 8250: Fix uninitialized variable warnings
 in pci_oxsemi_tornado_get_divisor

On Fri, Apr 11, 2025 at 05:20:48PM +0530, Purva Yeshi wrote:
> Fix Smatch-detected issue:
> 
> drivers/tty/serial/8250/8250_pci.c:1233 pci_oxsemi_tornado_get_divisor()
> error: uninitialized symbol 'tcr'.
> drivers/tty/serial/8250/8250_pci.c:1234 pci_oxsemi_tornado_get_divisor()
> error: uninitialized symbol 'quot'.
> drivers/tty/serial/8250/8250_pci.c:1238 pci_oxsemi_tornado_get_divisor()
> error: uninitialized symbol 'quot'.
> drivers/tty/serial/8250/8250_pci.c:1242 pci_oxsemi_tornado_get_divisor()
> error: uninitialized symbol 'cpr'.
> drivers/tty/serial/8250/8250_pci.c:1252 pci_oxsemi_tornado_get_divisor()
> error: uninitialized symbol 'cpr'.
> 
> Fix uninitialized variable usage in pci_oxsemi_tornado_get_divisor() that
> was triggering sparse warnings and potential undefined behavior. The
> variables tcr, cpr, and quot were used before being explicitly assigned
> values, leading to smatch warning in multiple lines of the function.

Are you really sure?  If you follow through the logic, it looks fine to
me.  What am I missing?  And why doesn't gcc or clang catch this?

> Initialize quot to 1, tcr to 16, and cpr to OXSEMI_TORNADO_CPR_DEF at the
> point of declaration. This ensures safe fallback values are used when these
> variables are not conditionally set later in the function, avoiding
> uninitialized access.

Where did these magic values come from?

thanks,

greg k-h