linux-kernel - Re: [PATCH 4/11] LTTng-core 0.5.108 : core

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]

Message-ID: <20060914153743.GC29906@Krystal>
Date:	Thu, 14 Sep 2006 11:37:43 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tom Zanussi <zanussi@...ibm.com>, ltt-dev@...fik.org,
	Michel Dagenais <michel.dagenais@...ymtl.ca>
Subject: Re: [PATCH 4/11] LTTng-core 0.5.108 : core

* Serge E. Hallyn (serue@...ibm.com) wrote:
> Hi,
> 
> I'm wondering why this is safe:
> 
> you grab references to the object which may be deleted after
> you drop the transport_list_lock at the top of this block.  Since
> a later patch shows the unregister being called right before the
> owning module is unloaded, that seems awefuly dangerous.
> 
> Is there some other magic going on making this safe?
> 

The ltt_traces_sem mutex is intended to make this safe. However, the transport
separation patch, contributed recently, uses its own transport_list_lock, which
seems to be broken.

I will fix it by using ltt_traces_sem around :


        down(&ltt_traces_sem);
        list_for_each_entry(tran, &ltt_transport_list, node) {
                if (!strcmp(tran->name, trace_type)) {
                        transport = tran;
                        break;
                }
        }

        if (!transport) {
                err = EINVAL;
                printk(KERN_ERR "LTT : Transport %s is not present.\n", trace_type);
                goto trace_error;
        }

        if(!try_module_get(transport->owner)) {
                err = ENODEV;
                printk(KERN_ERR "LTT : Can't lock transport module.\n");
                goto trace_error;
        }
        up(&ltt_traces_sem);

And change the transport_list_lock for ltt_traces_sem everywhere else.

Thanks for spotting this bug,

Mathieu


OpenPGP public key:              http://krystal.dyndns.org:8080/key/compudj.gpg
Key fingerprint:     8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68 
-
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/