From: "Anand H. Krishnan" <anandhkrishnan@yahoo.co.in>
To: Jesper Juhl <jesper.juhl@gmail.com>,
Ashutosh Naik <ashutosh.naik@gmail.com>
Cc: linux-kernel@vger.kernel.org, rusty@rustcorp.com.au,
rth@redhat.com, akpm@osdl.org, Greg KH <greg@kroah.com>,
anandhkrishnan@yahoo.co.in
Subject: Re: [RFC][PATCH] Prevent overriding of Symbols in the Kernel, avoiding Undefined behaviour
Date: Tue, 13 Dec 2005 00:23:50 -0800 (PST) [thread overview]
Message-ID: <20051213082350.11599.qmail@web8605.mail.in.yahoo.com> (raw)
In-Reply-To: <9a8748490512121425r63cba7axab114f80746ee066@mail.gmail.com>
Hi,
> I'm wondering, doesn't this take quite a long time?
> Too long to hold
> a spinlock for?
>
> Of course we need locking to prevent other module
> loads to modify the
> symbol table while we are checking this one, but to
> prevent the kernel
> from stalling everything else for a long time,
> wouldn't it be better
> to use a semaphore (we can sleep with those -
> right?) and an explicit
> schedule() call in the loop(s)? Or am I completely
> out in outere
> space with that thought?
>
Both at the time of loading a module and while
unloading a
module module_mutex is acquired. In the first place we
wer
e not planning to take the spinlock at all. But saw
that r
esolve_symbol does that and hence wasn't sure whether
the
lock should be acquired.
> Shouldn't this printk() be using KERN_ERROR ?
>
> printk(KERN_ERROR "%s: Duplicate Exported Symbol
> found in %s\n",
>
>
> > + strtab + index, mod->name);
> > + return -ENOEXEC;
> > +duplicate_gpl_sym:
> > + spin_unlock_irq(&modlist_lock);
> > + printk("%s: Duplicate Exported Symbol found in
> %s\n",
> > + strtab + index, mod->name);
> > + return -ENOEXEC;
> > +}
>
> Why 3 different exit paths? and 2 of them are even
> identical. Why not
> something like this instead? :
>
> {
> ...
> if (unlikely(value) {
> ret = -ENOEXEC;
> goto out;
> }
> ...
> out:
> spin_unlock_irq();
> if (ret)
> printk();
> return ret;
> }
>
We will send an updated patch with the modifications.
Thanks,
Anand
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next prev parent reply other threads:[~2005-12-13 8:27 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-12 12:39 [RFC][PATCH] Prevent overriding of Symbols in the Kernel, avoiding Undefined behaviour Ashutosh Naik
2005-12-12 12:44 ` Ashutosh Naik
2005-12-12 22:25 ` Jesper Juhl
2005-12-13 8:23 ` Anand H. Krishnan [this message]
2005-12-12 19:13 ` Andrew Morton
2005-12-12 19:27 ` Richard Henderson
2005-12-12 20:20 ` Greg KH
2005-12-12 20:30 ` Jesper Juhl
2005-12-12 22:48 ` Alan Cox
2005-12-13 8:03 ` Arjan van de Ven
2005-12-13 14:32 ` Ashutosh Naik
2005-12-12 22:01 ` Rusty Russell
2005-12-13 14:26 ` Ashutosh Naik
2005-12-13 15:28 ` Ashutosh Naik
2005-12-13 16:49 ` [RFC][PATCH] " Jesper Juhl
2005-12-14 2:03 ` Rusty Russell
2005-12-14 4:10 ` Ashutosh Naik
2005-12-14 5:02 ` Ashutosh Naik
2005-12-15 4:40 ` Andrew Morton
2005-12-15 5:15 ` Rusty Russell
2005-12-15 5:45 ` Ashutosh Naik
2005-12-14 5:46 ` Ashutosh Naik
2005-12-14 23:02 ` Rusty Russell
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