Media devnode open/ioctl could be in progress when media device unregister
is initiated. System calls and ioctls check media device registered status
at the beginning, however, there is a window where unregister could be in
progress without changing the media devnode status to unregistered.
process 1 process 2
fd = open(/dev/media0)
media_devnode_is_registered()
(returns true here)
media_device_unregister()
(unregister is in progress
and devnode isn't
unregistered yet)
...
ioctl(fd, ...)
__media_ioctl()
media_devnode_is_registered()
(returns true here)
...
media_devnode_unregister()
...
(driver releases the media device
memory)
media_device_ioctl()
(By this point
devnode->media_dev does not
point to allocated memory.
use-after free in in mutex_lock_nested)
BUG: KASAN: use-after-free in mutex_lock_nested+0x79c/0x800 at addr
ffff8801ebe914f0
Fix it by clearing register bit when unregister starts to avoid the race.
process 1 process 2
fd = open(/dev/media0)
media_devnode_is_registered()
(could return true here)
media_device_unregister()
(clear the register bit,
then start unregister.)
...
ioctl(fd, ...)
__media_ioctl()
media_devnode_is_registered()
(return false here, ioctl
returns I/O error, and
will not access media
device memory)
...
media_devnode_unregister()
...
(driver releases the media device
memory)
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reported-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Tested-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
When driver unbinds while media_ioctl is in progress, cdev_put() fails with
when app exits after driver unbinds.
Add devnode struct device kobj as the cdev parent kobject. cdev_add() gets
a reference to it and releases it in cdev_del() ensuring that the devnode
is not deallocated as long as the application has the device file open.
media_devnode_register() initializes the struct device kobj before calling
cdev_add(). media_devnode_unregister() does cdev_del() and then deletes the
device. devnode is released when the last reference to the struct device is
gone.
This problem is found on uvcvideo, em28xx, and au0828 drivers and fix has
been tested on all three.
kernel: [ 193.599736] BUG: KASAN: use-after-free in cdev_put+0x4e/0x50
kernel: [ 193.599745] Read of size 8 by task media_device_te/1851
kernel: [ 193.599792] INFO: Allocated in __media_device_register+0x54
kernel: [ 193.599951] INFO: Freed in media_devnode_release+0xa4/0xc0
kernel: [ 193.601083] Call Trace:
kernel: [ 193.601093] [<ffffffff81aecac3>] dump_stack+0x67/0x94
kernel: [ 193.601102] [<ffffffff815359b2>] print_trailer+0x112/0x1a0
kernel: [ 193.601111] [<ffffffff8153b5e4>] object_err+0x34/0x40
kernel: [ 193.601119] [<ffffffff8153d9d4>] kasan_report_error+0x224/0x530
kernel: [ 193.601128] [<ffffffff814a2c3d>] ? kzfree+0x2d/0x40
kernel: [ 193.601137] [<ffffffff81539d72>] ? kfree+0x1d2/0x1f0
kernel: [ 193.601154] [<ffffffff8157ca7e>] ? cdev_put+0x4e/0x50
kernel: [ 193.601162] [<ffffffff8157ca7e>] cdev_put+0x4e/0x50
kernel: [ 193.601170] [<ffffffff815767eb>] __fput+0x52b/0x6c0
kernel: [ 193.601179] [<ffffffff8117743a>] ? switch_task_namespaces+0x2a
kernel: [ 193.601188] [<ffffffff815769ee>] ____fput+0xe/0x10
kernel: [ 193.601196] [<ffffffff81170023>] task_work_run+0x133/0x1f0
kernel: [ 193.601204] [<ffffffff8117746e>] ? switch_task_namespaces+0x5e
kernel: [ 193.601213] [<ffffffff8111b50c>] do_exit+0x72c/0x2c20
kernel: [ 193.601224] [<ffffffff8111ade0>] ? release_task+0x1250/0x1250
-
-
-
kernel: [ 193.601360] [<ffffffff81003587>] ? exit_to_usermode_loop+0xe7
kernel: [ 193.601368] [<ffffffff810035c0>] exit_to_usermode_loop+0x120
kernel: [ 193.601376] [<ffffffff810061da>] syscall_return_slowpath+0x16a
kernel: [ 193.601386] [<ffffffff82848b33>] entry_SYSCALL_64_fastpath+0xa6
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Tested-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
struct media_devnode is currently embedded at struct media_device.
While this works fine during normal usage, it leads to a race
condition during devnode unregister. the problem is that drivers
assume that, after calling media_device_unregister(), the struct
that contains media_device can be freed. This is not true, as it
can't be freed until userspace closes all opened /dev/media devnodes.
In other words, if the media devnode is still open, and media_device
gets freed, any call to an ioctl will make the core to try to access
struct media_device, with will cause an use-after-free and even GPF.
Fix this by dynamically allocating the struct media_devnode and only
freeing it when it is safe.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Along all media controller code, "mdev" is used to represent
a pointer to struct media_device, and "devnode" for a pointer
to struct media_devnode.
However, inside media-devnode.[ch], "mdev" is used to represent
a pointer to struct media_devnode.
This is very confusing and may lead to development errors.
So, let's change all occurrences at media-devnode.[ch] to
also use "devnode" for such pointers.
This patch doesn't make any functional changes.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Callbacks invoked from put_device() may free the struct media_devnode
pointer, so any cleanup needs to be done before put_device().
Signed-off-by: Max Kellermann <max@duempel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
We should protect the device unregister patch too, at the error
condition.
Signed-off-by: Max Kellermann <max@duempel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
As we're using the headers file only for documentation, move the
two kernel-doc macros to the header, and fix it to avoid
warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Instead of allocating a var to store 0 and just return it,
change the code to return 0 directly.
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
mdev->fops->owner is actually the owner of the very same module which
implements media_device_register(), so it can't be unloaded anyway. Instead,
use THIS_MODULE through a macro as does video_register_device().
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
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Merge tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system
Pull "Disintegrate and delete asm/system.h" from David Howells:
"Here are a bunch of patches to disintegrate asm/system.h into a set of
separate bits to relieve the problem of circular inclusion
dependencies.
I've built all the working defconfigs from all the arches that I can
and made sure that they don't break.
The reason for these patches is that I recently encountered a circular
dependency problem that came about when I produced some patches to
optimise get_order() by rewriting it to use ilog2().
This uses bitops - and on the SH arch asm/bitops.h drags in
asm-generic/get_order.h by a circuituous route involving asm/system.h.
The main difficulty seems to be asm/system.h. It holds a number of
low level bits with no/few dependencies that are commonly used (eg.
memory barriers) and a number of bits with more dependencies that
aren't used in many places (eg. switch_to()).
These patches break asm/system.h up into the following core pieces:
(1) asm/barrier.h
Move memory barriers here. This already done for MIPS and Alpha.
(2) asm/switch_to.h
Move switch_to() and related stuff here.
(3) asm/exec.h
Move arch_align_stack() here. Other process execution related bits
could perhaps go here from asm/processor.h.
(4) asm/cmpxchg.h
Move xchg() and cmpxchg() here as they're full word atomic ops and
frequently used by atomic_xchg() and atomic_cmpxchg().
(5) asm/bug.h
Move die() and related bits.
(6) asm/auxvec.h
Move AT_VECTOR_SIZE_ARCH here.
Other arch headers are created as needed on a per-arch basis."
Fixed up some conflicts from other header file cleanups and moving code
around that has happened in the meantime, so David's testing is somewhat
weakened by that. We'll find out anything that got broken and fix it..
* tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system: (38 commits)
Delete all instances of asm/system.h
Remove all #inclusions of asm/system.h
Add #includes needed to permit the removal of asm/system.h
Move all declarations of free_initmem() to linux/mm.h
Disintegrate asm/system.h for OpenRISC
Split arch_align_stack() out from asm-generic/system.h
Split the switch_to() wrapper out of asm-generic/system.h
Move the asm-generic/system.h xchg() implementation to asm-generic/cmpxchg.h
Create asm-generic/barrier.h
Make asm-generic/cmpxchg.h #include asm-generic/cmpxchg-local.h
Disintegrate asm/system.h for Xtensa
Disintegrate asm/system.h for Unicore32 [based on ver #3, changed by gxt]
Disintegrate asm/system.h for Tile
Disintegrate asm/system.h for Sparc
Disintegrate asm/system.h for SH
Disintegrate asm/system.h for Score
Disintegrate asm/system.h for S390
Disintegrate asm/system.h for PowerPC
Disintegrate asm/system.h for PA-RISC
Disintegrate asm/system.h for MN10300
...
Remove all #inclusions of asm/system.h preparatory to splitting and killing
it. Performed with the following command:
perl -p -i -e 's!^#\s*include\s*<asm/system[.]h>.*\n!!' `grep -Irl '^#\s*include\s*<asm/system[.]h>' *`
Signed-off-by: David Howells <dhowells@redhat.com>
Media-related drivers living outside drivers/media/ (such as the UVC
gadget driver in drivers/usb/gadget/) rely on the media core being
initialized before they're probed. As drivers/usb/ is linked before
drivers/media/, this is currently not the case and will lead to crashes
if the drivers are not compiled as modules.
Register media_devnode_init() as a subsys_initcall() instead of
module_init() to fix this.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Bhupesh Sharma <bhupesh.sharma@st.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Tested-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
The find_next_zero_bit() is called with the from and to arguments in the
wrong order. This results in the function always returning 0, and all
media devices being registered with minor 0. Furthermore, mdev->minor is
then used before being assigned with the find_next_zero_bit() return
value. This really makes sure we'll always use minor 0.
Fix this and let the system support more than one media device.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
The media_devnode structure provides support for registering and
unregistering character devices using a dynamic major number. Reference
counting is handled internally, making device drivers easier to write
without having to solve the open/disconnect race condition issue over
and over again.
The code is based on video/v4l2-dev.c.
[mchehab@redhat.com: Remove linux/smp_lock.h include to not break compilation on bisect]
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
