[PATCH v4] videobuf2: Add missing lock held on vb2_fop_relase
Ricardo Ribalda Delgado
ricardo.ribalda at gmail.com
Mon Nov 4 08:54:10 EST 2013
Hello Hans
Thanks for your comments.
Please take a look to v4 of this patch
https://patchwork.linuxtv.org/patch/20529/
On Mon, Nov 4, 2013 at 1:37 PM, Hans Verkuil <hverkuil at xs4all.nl> wrote:
> On 11/02/2013 10:53 AM, Ricardo Ribalda Delgado wrote:
>> From: Ricardo Ribalda <ricardo.ribalda at gmail.com>
>>
>> vb2_fop_relase does not held the lock although it is modifying the
>> queue->owner field.
>>
>> This could lead to race conditions on the vb2_perform_io function
>> when multiple applications are accessing the video device via
>> read/write API:
>
> It's also called directly by drivers/media/usb/em28xx/em28xx-video.c!
>
em28xx-video does not hold the lock, therefore it can call the normal
function. On v2 we made a internal function that should be called if
the funciton is called directly by the driver. Please take a look to
the old comments. https://patchwork.linuxtv.org/patch/20460/
>>
>> [ 308.297741] BUG: unable to handle kernel NULL pointer dereference at
>> 0000000000000260
>> [ 308.297759] IP: [<ffffffffa07a9fd2>] vb2_perform_fileio+0x372/0x610
>> [videobuf2_core]
>> [ 308.297794] PGD 159719067 PUD 158119067 PMD 0
>> [ 308.297812] Oops: 0000 #1 SMP
>> [ 308.297826] Modules linked in: qt5023_video videobuf2_dma_sg
>> qtec_xform videobuf2_vmalloc videobuf2_memops videobuf2_core
>> qtec_white qtec_mem gpio_xilinx qtec_cmosis qtec_pcie fglrx(PO)
>> spi_xilinx spi_bitbang qt5023
>> [ 308.297888] CPU: 1 PID: 2189 Comm: java Tainted: P O 3.11.0-qtec-standard #1
>> [ 308.297919] Hardware name: QTechnology QT5022/QT5022, BIOS
>> PM_2.1.0.309 X64 05/23/2013
>> [ 308.297952] task: ffff8801564e1690 ti: ffff88014dc02000 task.ti:
>> ffff88014dc02000
>> [ 308.297962] RIP: 0010:[<ffffffffa07a9fd2>] [<ffffffffa07a9fd2>]
>> vb2_perform_fileio+0x372/0x610 [videobuf2_core]
>> [ 308.297985] RSP: 0018:ffff88014dc03df8 EFLAGS: 00010202
>> [ 308.297995] RAX: 0000000000000000 RBX: ffff880158a23000 RCX: dead000000100100
>> [ 308.298003] RDX: 0000000000000000 RSI: dead000000200200 RDI: 0000000000000000
>> [ 308.298012] RBP: ffff88014dc03e58 R08: 0000000000000000 R09: 0000000000000001
>> [ 308.298020] R10: ffffea00051e8380 R11: ffff88014dc03fd8 R12: ffff880158a23070
>> [ 308.298029] R13: ffff8801549040b8 R14: 0000000000198000 R15: 0000000001887e60
>> [ 308.298040] FS: 00007f65130d5700(0000) GS:ffff88015ed00000(0000)
>> knlGS:0000000000000000
>> [ 308.298049] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 308.298057] CR2: 0000000000000260 CR3: 0000000159630000 CR4: 00000000000007e0
>> [ 308.298064] Stack:
>> [ 308.298071] ffff880156416c00 0000000000198000 0000000000000000
>> ffff880100000001
>> [ 308.298087] ffff88014dc03f50 00000000810a79ca 0002000000000001
>> ffff880154904718
>> [ 308.298101] ffff880156416c00 0000000000198000 ffff880154904338
>> ffff88014dc03f50
>> [ 308.298116] Call Trace:
>> [ 308.298143] [<ffffffffa07aa3c4>] vb2_read+0x14/0x20 [videobuf2_core]
>> [ 308.298198] [<ffffffffa07aa494>] vb2_fop_read+0xc4/0x120 [videobuf2_core]
>> [ 308.298252] [<ffffffff8154ee9e>] v4l2_read+0x7e/0xc0
>> [ 308.298296] [<ffffffff8116e639>] vfs_read+0xa9/0x160
>> [ 308.298312] [<ffffffff8116e882>] SyS_read+0x52/0xb0
>> [ 308.298328] [<ffffffff81784179>] tracesys+0xd0/0xd5
>> [ 308.298335] Code: e5 d6 ff ff 83 3d be 24 00 00 04 89 c2 4c 8b 45 b0
>> 44 8b 4d b8 0f 8f 20 02 00 00 85 d2 75 32 83 83 78 03 00 00 01 4b 8b
>> 44 c5 48 <8b> 88 60 02 00 00 85 c9 0f 84 b0 00 00 00 8b 40 58 89 c2 41
>> 89
>> [ 308.298487] RIP [<ffffffffa07a9fd2>] vb2_perform_fileio+0x372/0x610
>> [videobuf2_core]
>> [ 308.298507] RSP <ffff88014dc03df8>
>> [ 308.298514] CR2: 0000000000000260
>> [ 308.298526] ---[ end trace e8f01717c96d1e41 ]---
>>
>> Signed-off-by: Ricardo Ribalda <ricardo.ribalda at gmail.com>
>> ---
>> v2: Comments by Sylvester Nawrocki
>>
>> fimc-capture and fimc-lite where calling vb2_fop_release with the lock held.
>> Therefore a new __vb2_fop_release function has been created to be used by
>> drivers that overload the release function.
>>
>> v3: Comments by Sylvester Nawrocki and Mauro Carvalho Chehab
>>
>> Use vb2_fop_release_locked instead of __vb2_fop_release
>>
>> v4: Comments by Sylvester Nawrocki
>>
>> Rename vb2_fop_release_locked to __vb2_fop_release and fix patch format
>>
>> drivers/media/platform/exynos4-is/fimc-capture.c | 2 +-
>> drivers/media/platform/exynos4-is/fimc-lite.c | 2 +-
>> drivers/media/v4l2-core/videobuf2-core.c | 23 ++++++++++++++++++++++-
>> include/media/videobuf2-core.h | 1 +
>> 4 files changed, 25 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/media/platform/exynos4-is/fimc-capture.c b/drivers/media/platform/exynos4-is/fimc-capture.c
>> index fb27ff7..8192fe0 100644
>> --- a/drivers/media/platform/exynos4-is/fimc-capture.c
>> +++ b/drivers/media/platform/exynos4-is/fimc-capture.c
>> @@ -549,7 +549,7 @@ static int fimc_capture_release(struct file *file)
>> vc->streaming = false;
>> }
>>
>> - ret = vb2_fop_release(file);
>> + ret = __vb2_fop_release(file);
>>
>> if (close) {
>> clear_bit(ST_CAPT_BUSY, &fimc->state);
>> diff --git a/drivers/media/platform/exynos4-is/fimc-lite.c b/drivers/media/platform/exynos4-is/fimc-lite.c
>> index e5798f7..cbe51cd 100644
>> --- a/drivers/media/platform/exynos4-is/fimc-lite.c
>> +++ b/drivers/media/platform/exynos4-is/fimc-lite.c
>> @@ -546,7 +546,7 @@ static int fimc_lite_release(struct file *file)
>> mutex_unlock(&entity->parent->graph_mutex);
>> }
>>
>> - vb2_fop_release(file);
>> + __vb2_fop_release(file);
>> pm_runtime_put(&fimc->pdev->dev);
>> clear_bit(ST_FLITE_SUSPENDED, &fimc->state);
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
>> index 594c75e..f48d72a 100644
>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
>> @@ -2619,18 +2619,39 @@ int vb2_fop_mmap(struct file *file, struct vm_area_struct *vma)
>> }
>> EXPORT_SYMBOL_GPL(vb2_fop_mmap);
>>
>> -int vb2_fop_release(struct file *file)
>> +static int _vb2_fop_release(struct file *file, bool lock_is_held)
>> {
>> struct video_device *vdev = video_devdata(file);
>> + struct mutex *lock;
>>
>> if (file->private_data == vdev->queue->owner) {
>> + if (lock_is_held)
>> + lock = NULL;
>> + else
>> + lock = vdev->queue->lock ?
>> + vdev->queue->lock : vdev->lock;
>> + if (lock)
>> + mutex_lock(lock);
>> vb2_queue_release(vdev->queue);
>> vdev->queue->owner = NULL;
>> + if (lock)
>> + mutex_unlock(lock);
>> }
>> return v4l2_fh_release(file);
>> }
>> +
>> +int vb2_fop_release(struct file *file)
>> +{
>> + return _vb2_fop_release(file, false);
>> +}
>> EXPORT_SYMBOL_GPL(vb2_fop_release);
>>
>> +int __vb2_fop_release(struct file *file)
>> +{
>> + return _vb2_fop_release(file, true);
>> +}
>> +EXPORT_SYMBOL_GPL(__vb2_fop_release);
>
> Sorry for introducing yet another opinion, but I think this is very confusing.
It is confusing the lock_held parameter or the __ naming for unlocked versions?
>
> I would do this:
>
> static int __vb2_fop_release(struct file *file, struct mutex *lock)
> {
> struct video_device *vdev = video_devdata(file);
>
> if (file->private_data == vdev->queue->owner) {
> if (lock)
> mutex_lock(lock);
> vb2_queue_release(vdev->queue);
> vdev->queue->owner = NULL;
> if (lock)
> mutex_unlock(lock);
> }
> return v4l2_fh_release(file);
> }
>
> int vb2_fop_release(struct file *file)
> {
> struct video_device *vdev = video_devdata(file);
> struct mutex *lock = vdev->queue->lock ?
> vdev->queue->lock : vdev->lock;
>
> return __vb2_fop_release(file, lock);
> }
> EXPORT_SYMBOL_GPL(vb2_fop_release);
>
> int vb2_fop_release_unlock(struct file *file)
> {
> return __vb2_fop_release(file, NULL);
> }
> EXPORT_SYMBOL_GPL(vb2_fop_release_unlock);
>
> Optionally, __vb2_fop_release can be exported and then vb2_fop_release_unlock
> isn't necessary.
>
i dont have any strong opinion in any direction. All I really care is
that the oops is fixed :).
If your concern about the patch is the is_lock_held function, I can
make a patch with the params on your proposal and the __naming as
Sylvester suggested, so everyone is happy.
Sylvester, Hanshat do you think?
Thanks for your comments!
> Regards,
>
> Hans
>
>> +
>> ssize_t vb2_fop_write(struct file *file, char __user *buf,
>> size_t count, loff_t *ppos)
>> {
>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>> index 6781258..76400fa 100644
>> --- a/include/media/videobuf2-core.h
>> +++ b/include/media/videobuf2-core.h
>> @@ -491,6 +491,7 @@ int vb2_ioctl_expbuf(struct file *file, void *priv,
>>
>> int vb2_fop_mmap(struct file *file, struct vm_area_struct *vma);
>> int vb2_fop_release(struct file *file);
>> +int __vb2_fop_release(struct file *file);
>> ssize_t vb2_fop_write(struct file *file, char __user *buf,
>> size_t count, loff_t *ppos);
>> ssize_t vb2_fop_read(struct file *file, char __user *buf,
>>
>
--
Ricardo Ribalda
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