On 11/04/2013 02:54 PM, Ricardo Ribalda Delgado wrote: > 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@xxxxxxxxx> wrote: >> On 11/02/2013 10:53 AM, Ricardo Ribalda Delgado wrote: >>> From: Ricardo Ribalda <ricardo.ribalda@xxxxxxxxx> >>> >>> 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/ static int em28xx_v4l2_close(struct file *filp) { struct em28xx_fh *fh = filp->private_data; struct em28xx *dev = fh->dev; int errCode; em28xx_videodbg("users=%d\n", dev->users); mutex_lock(&dev->lock); vb2_fop_release(filp); ... vb2_fop_release(filp) will, with your patch, also try to get dev->lock. Sylwester's comment re em28xx is incorrect. > >>> >>> [ 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@xxxxxxxxx> >>> --- >>> 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? The naming for the most part. Having a normal function, a '_' prefix and a '__' prefix is a bit over the top IMHO. I prefer to have a clearly named _unlock version. Regards, Hans > >> >> 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, >>> >> > > > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
