linux-kernel - debugfs vs. device removal

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: <20170119154841.GA6416@vader>
Date:   Thu, 19 Jan 2017 07:48:41 -0800
From:   Omar Sandoval <osandov@...ndov.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     Jiri Kosina <jikos@...nel.org>
Subject: debugfs vs. device removal

Hi,

In the block layer, we abuse sysfs to export some per-device debugging
information. I was looking into moving this to debugfs, but I realized
that debugfs doesn't have a mechanism to ensure that a file associated
with a device is safe to use when the device is removed. 

At a quick glance, HID has some per-device information in debugfs.
However, I don't see any sort of protection against a device being
removed. I was easily able to trigger an oops by reading from
/sys/kernel/debug/hid/*/rdesc in a loop and removing the USB device
(trace attached).

How can I safely export per-device debugging information to debugfs?

Thanks,
Omar

View attachment "oops.txt" of type "text/plain" (3193 bytes)