[PATCH] v4l2-dev: Fix race condition on __video_register_device
From: Ricardo Ribalda Delgado
Date: Tue Aug 13 2013 - 11:04:20 EST
When 2 devices are registered at the same time, in Part 2 both will get
the same minor number, making Part6 crash, because it cannot create a
create a device with a duplicated minor:
[ 7.157648] ------------[ cut here ]------------
[ 7.157666] WARNING: at fs/sysfs/dir.c:530 sysfs_add_one+0xbd/0xe0()
[ 7.157669] sysfs: cannot create duplicate filename '/dev/char/81:1'
[ 7.157672] Modules linked in: qtec_xform(+) qt5023_video(+) videobuf2_vmalloc videobuf2_dma_sg videobuf2_memops videobuf2_core gpio_xilinx(+) qtec_white qtec_cmosis(+) qtec_pcie qt5023
[ 7.157694] CPU: 0 PID: 120 Comm: systemd-udevd Not tainted 3.10.0-qtec-standard #8
[ 7.157698] Hardware name: QTechnology QT5022/QT5022, BIOS PM_2.1.0.309 X64 05/23/2013
[ 7.157702] 0000000000000009 ffff8801788358e8 ffffffff8176c487 ffff880178835928
[ 7.157707] ffffffff8106f6f0 ffff880175759770 00000000ffffffef ffff880175759930
[ 7.157712] ffff8801788359e8 ffff880178bff000 ffff880175759930 ffff880178835988
[ 7.157718] Call Trace:
[ 7.157728] [<ffffffff8176c487>] dump_stack+0x19/0x1b
[ 7.157735] [<ffffffff8106f6f0>] warn_slowpath_common+0x70/0xa0
[ 7.157740] [<ffffffff8106f7d6>] warn_slowpath_fmt+0x46/0x50
[ 7.157746] [<ffffffff81324b35>] ? strlcat+0x65/0x90
[ 7.157750] [<ffffffff811d516d>] sysfs_add_one+0xbd/0xe0
[ 7.157755] [<ffffffff811d5c6b>] sysfs_do_create_link_sd+0xdb/0x200
[ 7.157760] [<ffffffff811d5db1>] sysfs_create_link+0x21/0x40
[ 7.157765] [<ffffffff813e277b>] device_add+0x21b/0x6d0
[ 7.157772] [<ffffffff813f2985>] ? pm_runtime_init+0xe5/0xf0
[ 7.157776] [<ffffffff813e2c4e>] device_register+0x1e/0x30
[ 7.157782] [<ffffffff8153e8c3>] __video_register_device+0x313/0x610
[ 7.157791] [<ffffffffa00957c5>] qtec_xform_probe+0x465/0x7a4 [qtec_xform]
[ 7.157797] [<ffffffff813e7b13>] platform_drv_probe+0x43/0x80
[ 7.157802] [<ffffffff813e531a>] ? driver_sysfs_add+0x7a/0xb0
[ 7.157807] [<ffffffff813e584b>] driver_probe_device+0x8b/0x3a0
[ 7.157812] [<ffffffff813e5c0b>] __driver_attach+0xab/0xb0
[ 7.157816] [<ffffffff813e5b60>] ? driver_probe_device+0x3a0/0x3a0
[ 7.157820] [<ffffffff813e37fd>] bus_for_each_dev+0x5d/0xa0
[ 7.157825] [<ffffffff813e529e>] driver_attach+0x1e/0x20
[ 7.157829] [<ffffffff813e4d3e>] bus_add_driver+0x10e/0x280
[ 7.157833] [<ffffffffa0099000>] ? 0xffffffffa0098fff
[ 7.157837] [<ffffffffa0099000>] ? 0xffffffffa0098fff
[ 7.157842] [<ffffffff813e6317>] driver_register+0x77/0x170
[ 7.157848] [<ffffffff81151bcc>] ? __vunmap+0x9c/0x110
[ 7.157852] [<ffffffffa0099000>] ? 0xffffffffa0098fff
[ 7.157857] [<ffffffff813e7236>] platform_driver_register+0x46/0x50
[ 7.157863] [<ffffffffa0099010>] qtec_xform_plat_driver_init+0x10/0x12 [qtec_xform]
[ 7.157869] [<ffffffff810002ea>] do_one_initcall+0xea/0x1a0
[ 7.157875] [<ffffffff810cf1f1>] load_module+0x1a91/0x2630
[ 7.157880] [<ffffffff8133bee0>] ? ddebug_proc_show+0xe0/0xe0
[ 7.157887] [<ffffffff817760f2>] ? page_fault+0x22/0x30
[ 7.157892] [<ffffffff810cfe7a>] SyS_init_module+0xea/0x140
[ 7.157898] [<ffffffff8177e5b9>] tracesys+0xd0/0xd5
[ 7.157902] ---[ end trace 660cc3a65a4bf01b ]---
[ 7.157939] __video_register_device: device_register failed
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@xxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-dev.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index 5923c5d..3f75f99 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -873,6 +873,7 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
/* Should not happen since we thought this minor was free */
WARN_ON(video_device[vdev->minor] != NULL);
+ video_device[vdev->minor] = vdev;
vdev->index = get_index(vdev);
mutex_unlock(&videodev_lock);
@@ -936,9 +937,6 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
#endif
/* Part 6: Activate this minor. The char device can now be used. */
set_bit(V4L2_FL_REGISTERED, &vdev->flags);
- mutex_lock(&videodev_lock);
- video_device[vdev->minor] = vdev;
- mutex_unlock(&videodev_lock);
return 0;
@@ -946,6 +944,7 @@ cleanup:
mutex_lock(&videodev_lock);
if (vdev->cdev)
cdev_del(vdev->cdev);
+ video_device[vdev->minor] = NULL;
devnode_clear(vdev);
mutex_unlock(&videodev_lock);
/* Mark this video device as never having been registered. */
--
1.7.10.4
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