linux-kernel - Re: [PATCH] use mutex instead of semaphore in RocketPort driver

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-next>] [day] [month] [year] [list]

Message-id: <462E9885.1010605@shaw.ca>
Date:	Tue, 24 Apr 2007 17:53:41 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Matthias Kaehlcke <matthias.kaehlcke@...il.com>,
	Oliver Neukum <oneukum@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] use mutex instead of semaphore in RocketPort driver

Matthias Kaehlcke wrote:
> El Tue, Apr 24, 2007 at 07:53:04PM +0200 Oliver Neukum ha dit:
> 
>> Am Dienstag, 24. April 2007 19:49 schrieb Matthias Kaehlcke:
>>> @@ -1706,7 +1706,7 @@ static int rp_write(struct tty_struct *tty,
>>>         if (count <= 0 || rocket_paranoia_check(info, "rp_write"))
>>>                 return 0;
>>>  
>>> -       down_interruptible(&info->write_sem);
>>> +       mutex_lock_interruptible(&info->write_mtx);
>> This is a bug. It is also present in the current code, but nevertheless
>> it is a bug. If you use an interruptible lock, you must be ready to deal
>> with interrupts, which are ignored by this code.
> 
> i fear i don't have the experience/knowledge to fix this bug, thanks
> for your remark. 
> 
> i'm a bit confused now about the interruptible locks, i thought using
> them means that the process will be waked up when receiving a
> signal. what role are playing interrupts when using interruptible locks?

You are correct, interrupts aren't involved. However if the wait is 
interrupted by a signal, mutex_lock_interruptible will return a nonzero 
return code which needs to be checked for (and likely -ERESTARTSYS or 
-EINTR returned), otherwise the code will blindly continue as though it 
has locked the mutex even though it has not.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/