linux-kernel - drivers/char/ppdev -

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>] [day] [month] [year] [list]

Message-ID: <110bee96-0c4b-21dd-9298-932970657801@linuxfoundation.org>
Date:   Fri, 2 Oct 2020 15:01:33 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     sudipm.mukherjee@...il.com
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: drivers/char/ppdev -

Hi Sudip,

While looking at atomic_t usages and noticed a few potential
problem the way struct pp_struct: atomic_t irqc field

- There is inconsistencies the lock hold in this driver.

pp_do_mutex is help before pp_do_ioctl() is called.
static int pp_do_ioctl()
....

pp_do_mutex
        case PPCLRIRQ:
                 ret = atomic_read(&pp->irqc);
                 if (copy_to_user(argp, &ret, sizeof(ret)))
                         return -EFAULT;
                 atomic_sub(ret, &pp->irqc);
                 return 0;

This path seems safe as far as atomic_t overflow is concerned.

However, pp_poll(), pp_irq(), and pp_open() etc. don't hold
lock while pp_do_ioctl() path does.

Something to look into to see if this is safe. I see this
comment for pp_poll() /* No kernel lock held - fine */

Anyway, please take a look and see if this is indeed a problem.

thanks,
-- Shuah