diff options
author | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2013-08-09 08:11:25 -0300 |
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committer | Mauro Carvalho Chehab <m.chehab@samsung.com> | 2013-08-22 12:01:00 -0300 |
commit | a517cca6b24fc54ac209e44118ec8962051662e3 (patch) | |
tree | 166ea9f4abb6512fbf4585d0760239a9d666b664 /drivers/media/v4l2-core | |
parent | 1ac7fdeeb52b05e108713d1ccc63e714c2489717 (diff) |
[media] media: vb2: Fix potential deadlock in vb2_prepare_buffer
Commit b037c0fde22b1d3cd0b3c3717d28e54619fc1592 ("media: vb2: fix
potential deadlock in mmap vs. get_userptr handling") fixes an AB-BA
deadlock related to the mmap_sem and driver locks. The same deadlock can
occur in vb2_prepare_buffer(), fix it the same way.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
Diffstat (limited to 'drivers/media/v4l2-core')
-rw-r--r-- | drivers/media/v4l2-core/videobuf2-core.c | 52 |
1 files changed, 43 insertions, 9 deletions
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c index 35a5b8ff6a09..fb6802c667d3 100644 --- a/drivers/media/v4l2-core/videobuf2-core.c +++ b/drivers/media/v4l2-core/videobuf2-core.c @@ -1248,50 +1248,84 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b) */ int vb2_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b) { + struct rw_semaphore *mmap_sem = NULL; struct vb2_buffer *vb; int ret; + /* + * In case of user pointer buffers vb2 allocator needs to get direct + * access to userspace pages. This requires getting read access on + * mmap semaphore in the current process structure. The same + * semaphore is taken before calling mmap operation, while both mmap + * and prepare_buf are called by the driver or v4l2 core with driver's + * lock held. To avoid a AB-BA deadlock (mmap_sem then driver's lock in + * mmap and driver's lock then mmap_sem in prepare_buf) the videobuf2 + * core release driver's lock, takes mmap_sem and then takes again + * driver's lock. + * + * To avoid race with other vb2 calls, which might be called after + * releasing driver's lock, this operation is performed at the + * beggining of prepare_buf processing. This way the queue status is + * consistent after getting driver's lock back. + */ + if (q->memory == V4L2_MEMORY_USERPTR) { + mmap_sem = ¤t->mm->mmap_sem; + call_qop(q, wait_prepare, q); + down_read(mmap_sem); + call_qop(q, wait_finish, q); + } + if (q->fileio) { dprintk(1, "%s(): file io in progress\n", __func__); - return -EBUSY; + ret = -EBUSY; + goto unlock; } if (b->type != q->type) { dprintk(1, "%s(): invalid buffer type\n", __func__); - return -EINVAL; + ret = -EINVAL; + goto unlock; } if (b->index >= q->num_buffers) { dprintk(1, "%s(): buffer index out of range\n", __func__); - return -EINVAL; + ret = -EINVAL; + goto unlock; } vb = q->bufs[b->index]; if (NULL == vb) { /* Should never happen */ dprintk(1, "%s(): buffer is NULL\n", __func__); - return -EINVAL; + ret = -EINVAL; + goto unlock; } if (b->memory != q->memory) { dprintk(1, "%s(): invalid memory type\n", __func__); - return -EINVAL; + ret = -EINVAL; + goto unlock; } if (vb->state != VB2_BUF_STATE_DEQUEUED) { dprintk(1, "%s(): invalid buffer state %d\n", __func__, vb->state); - return -EINVAL; + ret = -EINVAL; + goto unlock; } ret = __verify_planes_array(vb, b); if (ret < 0) - return ret; + goto unlock; + ret = __buf_prepare(vb, b); if (ret < 0) - return ret; + goto unlock; __fill_v4l2_buffer(vb, b); - return 0; +unlock: + if (mmap_sem) + up_read(mmap_sem); + return ret; } EXPORT_SYMBOL_GPL(vb2_prepare_buf); |