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/ >> >> [ 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? > > 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 -- 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
