media: videobuf2-core: take mmap_lock in vb2_get_unmapped_area()

While vb2_mmap took the mmap_lock mutex, vb2_get_unmapped_area didn't.
Add this.

Also take this opportunity to move the 'q->memory != VB2_MEMORY_MMAP'
check and vb2_fileio_is_active() check into __find_plane_by_offset() so
both vb2_mmap and vb2_get_unmapped_area do the same checks.

Since q->memory is checked while mmap_lock is held, also take that lock
in reqbufs and create_bufs when it is set, and set it back to
MEMORY_UNKNOWN on error.

Fixes: f035eb4 ("[media] videobuf2: fix lockdep warning")
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Hans Verkuil

drivers/media/common/videobuf2/videobuf2-core.c

@@ -813,7 +813,13 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	num_buffers = max_t(unsigned int, *count, q->min_buffers_needed);
 	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
 	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
+	/*
+	 * Set this now to ensure that drivers see the correct q->memory value
+	 * in the queue_setup op.
+	 */
+	mutex_lock(&q->mmap_lock);
 	q->memory = memory;
+	mutex_unlock(&q->mmap_lock);
 	set_queue_coherency(q, non_coherent_mem);
 
 	/*
@@ -823,22 +829,27 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	ret = call_qop(q, queue_setup, q, &num_buffers, &num_planes,
 		       plane_sizes, q->alloc_devs);
 	if (ret)
-		return ret;
+		goto error;
 
 	/* Check that driver has set sane values */
-	if (WARN_ON(!num_planes))
-		return -EINVAL;
+	if (WARN_ON(!num_planes)) {
+		ret = -EINVAL;
+		goto error;
+	}
 
 	for (i = 0; i < num_planes; i++)
-		if (WARN_ON(!plane_sizes[i]))
-			return -EINVAL;
+		if (WARN_ON(!plane_sizes[i])) {
+			ret = -EINVAL;
+			goto error;
+		}
 
 	/* Finally, allocate buffers and video memory */
 	allocated_buffers =
 		__vb2_queue_alloc(q, memory, num_buffers, num_planes, plane_sizes);
 	if (allocated_buffers == 0) {
 		dprintk(q, 1, "memory allocation failed\n");
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto error;
 	}
 
 	/*
@@ -879,7 +890,8 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	if (ret < 0) {
 		/*
 		 * Note: __vb2_queue_free() will subtract 'allocated_buffers'
-		 * from q->num_buffers.
+		 * from q->num_buffers and it will reset q->memory to
+		 * VB2_MEMORY_UNKNOWN.
 		 */
 		__vb2_queue_free(q, allocated_buffers);
 		mutex_unlock(&q->mmap_lock);
@@ -895,6 +907,12 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
 	q->waiting_for_buffers = !q->is_output;
 
 	return 0;
+
+error:
+	mutex_lock(&q->mmap_lock);
+	q->memory = VB2_MEMORY_UNKNOWN;
+	mutex_unlock(&q->mmap_lock);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(vb2_core_reqbufs);
 
@@ -906,20 +924,27 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 	unsigned int num_planes = 0, num_buffers, allocated_buffers;
 	unsigned plane_sizes[VB2_MAX_PLANES] = { };
 	bool non_coherent_mem = flags & V4L2_MEMORY_FLAG_NON_COHERENT;
+	bool no_previous_buffers = !q->num_buffers;
 	int ret;
 
 	if (q->num_buffers == VB2_MAX_FRAME) {
 		dprintk(q, 1, "maximum number of buffers already allocated\n");
 		return -ENOBUFS;
 	}
 
-	if (!q->num_buffers) {
+	if (no_previous_buffers) {
 		if (q->waiting_in_dqbuf && *count) {
 			dprintk(q, 1, "another dup()ped fd is waiting for a buffer\n");
 			return -EBUSY;
 		}
 		memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
+		/*
+		 * Set this now to ensure that drivers see the correct q->memory
+		 * value in the queue_setup op.
+		 */
+		mutex_lock(&q->mmap_lock);
 		q->memory = memory;
+		mutex_unlock(&q->mmap_lock);
 		q->waiting_for_buffers = !q->is_output;
 		set_queue_coherency(q, non_coherent_mem);
 	} else {
@@ -945,14 +970,15 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 	ret = call_qop(q, queue_setup, q, &num_buffers,
 		       &num_planes, plane_sizes, q->alloc_devs);
 	if (ret)
-		return ret;
+		goto error;
 
 	/* Finally, allocate buffers and video memory */
 	allocated_buffers = __vb2_queue_alloc(q, memory, num_buffers,
 				num_planes, plane_sizes);
 	if (allocated_buffers == 0) {
 		dprintk(q, 1, "memory allocation failed\n");
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto error;
 	}
 
 	/*
@@ -983,7 +1009,8 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 	if (ret < 0) {
 		/*
 		 * Note: __vb2_queue_free() will subtract 'allocated_buffers'
-		 * from q->num_buffers.
+		 * from q->num_buffers and it will reset q->memory to
+		 * VB2_MEMORY_UNKNOWN.
 		 */
 		__vb2_queue_free(q, allocated_buffers);
 		mutex_unlock(&q->mmap_lock);
@@ -998,6 +1025,14 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
 	*count = allocated_buffers;
 
 	return 0;
+
+error:
+	if (no_previous_buffers) {
+		mutex_lock(&q->mmap_lock);
+		q->memory = VB2_MEMORY_UNKNOWN;
+		mutex_unlock(&q->mmap_lock);
+	}
+	return ret;
 }
 EXPORT_SYMBOL_GPL(vb2_core_create_bufs);
 
@@ -2164,6 +2199,22 @@ static int __find_plane_by_offset(struct vb2_queue *q, unsigned long off,
 	struct vb2_buffer *vb;
 	unsigned int buffer, plane;
 
+	/*
+	 * Sanity checks to ensure the lock is held, MEMORY_MMAP is
+	 * used and fileio isn't active.
+	 */
+	lockdep_assert_held(&q->mmap_lock);
+
+	if (q->memory != VB2_MEMORY_MMAP) {
+		dprintk(q, 1, "queue is not currently set up for mmap\n");
+		return -EINVAL;
+	}
+
+	if (vb2_fileio_is_active(q)) {
+		dprintk(q, 1, "file io in progress\n");
+		return -EBUSY;
+	}
+
 	/*
 	 * Go over all buffers and their planes, comparing the given offset
 	 * with an offset assigned to each plane. If a match is found,
@@ -2265,11 +2316,6 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
 	int ret;
 	unsigned long length;
 
-	if (q->memory != VB2_MEMORY_MMAP) {
-		dprintk(q, 1, "queue is not currently set up for mmap\n");
-		return -EINVAL;
-	}
-
 	/*
 	 * Check memory area access mode.
 	 */
@@ -2291,14 +2337,9 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
 
 	mutex_lock(&q->mmap_lock);
 
-	if (vb2_fileio_is_active(q)) {
-		dprintk(q, 1, "mmap: file io in progress\n");
-		ret = -EBUSY;
-		goto unlock;
-	}
-
 	/*
-	 * Find the plane corresponding to the offset passed by userspace.
+	 * Find the plane corresponding to the offset passed by userspace. This
+	 * will return an error if not MEMORY_MMAP or file I/O is in progress.
 	 */
 	ret = __find_plane_by_offset(q, off, &buffer, &plane);
 	if (ret)
@@ -2351,22 +2392,25 @@ unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
 	void *vaddr;
 	int ret;
 
-	if (q->memory != VB2_MEMORY_MMAP) {
-		dprintk(q, 1, "queue is not currently set up for mmap\n");
-		return -EINVAL;
-	}
+	mutex_lock(&q->mmap_lock);
 
 	/*
-	 * Find the plane corresponding to the offset passed by userspace.
+	 * Find the plane corresponding to the offset passed by userspace. This
+	 * will return an error if not MEMORY_MMAP or file I/O is in progress.
 	 */
 	ret = __find_plane_by_offset(q, off, &buffer, &plane);
 	if (ret)
-		return ret;
+		goto unlock;
 
 	vb = q->bufs[buffer];
 
 	vaddr = vb2_plane_vaddr(vb, plane);
+	mutex_unlock(&q->mmap_lock);
 	return vaddr ? (unsigned long)vaddr : -EINVAL;
+
+unlock:
+	mutex_unlock(&q->mmap_lock);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(vb2_get_unmapped_area);
 #endif