From patchwork Mon Aug 6 17:06:48 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [SRU, Oneiric/Precise, Quantal, media] Avoid sysfs oops when an rc_dev's raw device is absent Date: Mon, 06 Aug 2012 07:06:48 -0000 From: Herton Ronaldo Krzesinski X-Patchwork-Id: 175401 Message-Id: <1344272808-7953-1-git-send-email-herton.krzesinski@canonical.com> To: kernel-team@lists.ubuntu.com From: Douglas Bagnall For some reason, when the lirc daemon learns that a usb remote control has been unplugged, it wants to read the sysfs attributes of the disappearing device. This is useful for uncovering transient inconsistencies, but less so for keeping the system running when such inconsistencies exist. Under some circumstances (like every time I unplug my dvb stick from my laptop), lirc catches an rc_dev whose raw event handler has been removed (presumably by ir_raw_event_unregister), and proceeds to interrogate the raw protocols supported by the NULL pointer. This patch avoids the NULL dereference, and ignores the issue of how this state of affairs came about in the first place. Version 2 incorporates changes recommended by Mauro Carvalho Chehab (-ENODEV instead of -EINVAL, and a signed-off-by). Signed-off-by: Douglas Bagnall Signed-off-by: Mauro Carvalho Chehab (cherry picked from commit 720bb6436ff30fccad05cf5bdf961ea5b1f5686d upstream) BugLink: http://bugs.launchpad.net/bugs/1015836 Signed-off-by: Herton Ronaldo Krzesinski Acked-by: Leann Ogasawara --- drivers/media/rc/rc-main.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) Bug was reported against Precise, but looking at the code Oneiric seems affected as well. Natty would be affected too, but seems its code have more problems (for example, it misses commit 08aeb7c "rc: add locking to fix register/show race"), and I'm not sure it's worth touching Natty at this stage. I did a quick verification against one of the oopses on the bug also, the patch looks good (code patched will address crash matched with symbols from linux-image-3.2.0-26-generic-dbgsym_3.2.0-26.41_amd64.ddeb). And seems a fix that is worth for stable upstream too, I'll send it there as well. diff --git a/drivers/media/rc/rc-main.c b/drivers/media/rc/rc-main.c index 6e16b09..cabc19c 100644 --- a/drivers/media/rc/rc-main.c +++ b/drivers/media/rc/rc-main.c @@ -775,10 +775,11 @@ static ssize_t show_protocols(struct device *device, if (dev->driver_type == RC_DRIVER_SCANCODE) { enabled = dev->rc_map.rc_type; allowed = dev->allowed_protos; - } else { + } else if (dev->raw) { enabled = dev->raw->enabled_protocols; allowed = ir_raw_get_allowed_protocols(); - } + } else + return -ENODEV; IR_dprintk(1, "allowed - 0x%llx, enabled - 0x%llx\n", (long long)allowed,