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Subject[PATCH v2 2/2] media: dvb-usb: Fix use-after-free access
Date
dvb_usb_device_init() copies the properties to the own data, so that
the callers can release the original properties later (as done in the
commit 299c7007e936 "media: dw2102: Fix memleak on sequence of
probes"). However, it also stores dev->desc pointer that is a
reference to the original properties data. Since dev->desc is
referred later, it may result in use-after-free, in the worst case,
leading to a kernel Oops as reported.

This patch addresses the problem by allocating and copying the
properties at first, then get the desc from the copied properties.

Reported-and-tested-by: Stefan Seyfried <seife+kernel@b1-systems.com>
BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1181104
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
v1->v2: Only tag update

drivers/media/usb/dvb-usb/dvb-usb-init.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
index c78158d12540..12983baf6c3f 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
@@ -264,27 +264,30 @@ int dvb_usb_device_init(struct usb_interface *intf,
if (du != NULL)
*du = NULL;

- if ((desc = dvb_usb_find_device(udev, props, &cold)) == NULL) {
+ d = kzalloc(sizeof(struct dvb_usb_device), GFP_KERNEL);
+ if (!d) {
+ err("no memory for 'struct dvb_usb_device'");
+ return -ENOMEM;
+ }
+
+ memcpy(&d->props, props, sizeof(struct dvb_usb_device_properties));
+
+ desc = dvb_usb_find_device(udev, &d->props, &cold);
+ if (!desc) {
deb_err("something went very wrong, device was not found in current device list - let's see what comes next.\n");
- return -ENODEV;
+ ret = -ENODEV;
+ goto error;
}

if (cold) {
info("found a '%s' in cold state, will try to load a firmware", desc->name);
ret = dvb_usb_download_firmware(udev, props);
if (!props->no_reconnect || ret != 0)
- return ret;
+ goto error;
}

info("found a '%s' in warm state.", desc->name);
- d = kzalloc(sizeof(struct dvb_usb_device), GFP_KERNEL);
- if (d == NULL) {
- err("no memory for 'struct dvb_usb_device'");
- return -ENOMEM;
- }
-
d->udev = udev;
- memcpy(&d->props, props, sizeof(struct dvb_usb_device_properties));
d->desc = desc;
d->owner = owner;

--
2.26.2
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