linux-kernel - Re: BKL still required for what functions?

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

Date:	Tue, 7 Oct 2008 11:55:27 -0600
From:	Richard Holden <aciddeath@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: BKL still required for what functions?


On Oct 7, 2008, at 10:35 AM, Alan Cox wrote:
>
> Its never so simple - a lot of the functions it depends what data  
> you are
> using or passing to them whether they are BKL safe.
>
> Which bits use the BKL and what do you need to know is safe ?

Actually, it looks like I was looking at 2 different places, the  
simple removal is in phonedev.c that you authored, as far as I can  
tell the only thing the BKL is protecting is a call to request_module,  
it may be some nesting rules that I don't understand but I think if it  
is still needed there we could push the lock_kernel call down to the  
site of the request_module call. See patch below.

Thanks,
Richard Holden

Signed-off-by: Richard Holden <aciddeath@...il.com>

diff --git a/drivers/telephony/phonedev.c b/drivers/telephony/phonedev.c
index 4d74ba3..fd1424c 100644
--- a/drivers/telephony/phonedev.c
+++ b/drivers/telephony/phonedev.c
@@ -54,14 +54,16 @@ static int phone_open(struct inode *inode, struct  
file *file)
  	if (minor >= PHONE_NUM_DEVICES)
  		return -ENODEV;

-	lock_kernel();
+	
  	mutex_lock(&phone_lock);
  	p = phone_device[minor];
  	if (p)
  		new_fops = fops_get(p->f_op);
  	if (!new_fops) {
  		mutex_unlock(&phone_lock);
+		lock_kernel();
  		request_module("char-major-%d-%d", PHONE_MAJOR, minor);
+		unlock_kernel();
  		mutex_lock(&phone_lock);
  		p = phone_device[minor];
  		if (p == NULL || (new_fops = fops_get(p->f_op)) == NULL)
@@ -81,7 +83,6 @@ static int phone_open(struct inode *inode, struct  
file *file)
  	fops_put(old_fops);
  end:
  	mutex_unlock(&phone_lock);
-	unlock_kernel();
  	return err;
  }


--
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/