[media] vb2: fix nasty vb2_thread regression

The vb2_thread implementation was made generic and was moved from
videobuf2-v4l2.c to videobuf2-core.c in commit af3bac1a. Unfortunately
that clearly was never tested since it broke read() causing NULL address
references.

The root cause was confused handling of vb2_buffer vs v4l2_buffer (the pb
pointer in various core functions).

The v4l2_buffer no longer exists after moving the code into the core and
it is no longer needed. However, the vb2_thread code passed a pointer to
a vb2_buffer to the core functions were a v4l2_buffer pointer was expected
and vb2_thread expected that the vb2_buffer fields would be filled in
correctly.

This is obviously wrong since v4l2_buffer != vb2_buffer. Note that the
pb pointer is a void pointer, so no type-checking took place.

This patch fixes this problem:

1) allow pb to be NULL for vb2_core_(d)qbuf. The vb2_thread code will use
   a NULL pointer here since they don't care about v4l2_buffer anyway.
2) let vb2_core_dqbuf pass back the index of the received buffer. This is
   all vb2_thread needs: this index is the index into the q->bufs array
   and vb2_thread just gets the vb2_buffer from there.
3) the fileio->b pointer (that originally contained a v4l2_buffer) is
   removed altogether since it is no longer needed.

Tested with vivid and the cobalt driver.

Cc: stable@vger.kernel.org # Kernel >= 4.3
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reported-by: Matthias Schwarzott <zzam@gentoo.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

2 files changed, 44 insertions, 53 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index c5d49d7a0d76..b53e42c329cb 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1063,8 +1063,11 @@ EXPORT_SYMBOL_GPL(vb2_discard_done);
  */
 static int __qbuf_mmap(struct vb2_buffer *vb, const void *pb)
 {
-        int ret = call_bufop(vb->vb2_queue, fill_vb2_buffer,
-                        vb, pb, vb->planes);
+        int ret = 0;
+
+        if (pb)
+                ret = call_bufop(vb->vb2_queue, fill_vb2_buffer,
+                                 vb, pb, vb->planes);
         return ret ? ret : call_vb_qop(vb, buf_prepare, vb);
 }
 
@@ -1077,14 +1080,16 @@ static int __qbuf_userptr(struct vb2_buffer *vb, const void *pb)
         struct vb2_queue *q = vb->vb2_queue;
         void *mem_priv;
         unsigned int plane;
-        int ret;
+        int ret = 0;
         enum dma_data_direction dma_dir =
                 q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
         bool reacquired = vb->planes[0].mem_priv == NULL;
 
         memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
         /* Copy relevant information provided by the userspace */
-        ret = call_bufop(vb->vb2_queue, fill_vb2_buffer, vb, pb, planes);
+        if (pb)
+                ret = call_bufop(vb->vb2_queue, fill_vb2_buffer,
+                                 vb, pb, planes);
         if (ret)
                 return ret;
 
@@ -1192,14 +1197,16 @@ static int __qbuf_dmabuf(struct vb2_buffer *vb, const void *pb)
         struct vb2_queue *q = vb->vb2_queue;
         void *mem_priv;
         unsigned int plane;
-        int ret;
+        int ret = 0;
         enum dma_data_direction dma_dir =
                 q->is_output ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
         bool reacquired = vb->planes[0].mem_priv == NULL;
 
         memset(planes, 0, sizeof(planes[0]) * vb->num_planes);
         /* Copy relevant information provided by the userspace */
-        ret = call_bufop(vb->vb2_queue, fill_vb2_buffer, vb, pb, planes);
+        if (pb)
+                ret = call_bufop(vb->vb2_queue, fill_vb2_buffer,
+                                 vb, pb, planes);
         if (ret)
                 return ret;
 
@@ -1520,7 +1527,8 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
         q->waiting_for_buffers = false;
         vb->state = VB2_BUF_STATE_QUEUED;
 
-        call_void_bufop(q, copy_timestamp, vb, pb);
+        if (pb)
+                call_void_bufop(q, copy_timestamp, vb, pb);
 
         trace_vb2_qbuf(q, vb);
 
@@ -1532,7 +1540,8 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
                 __enqueue_in_driver(vb);
 
         /* Fill buffer information for the userspace */
-        call_void_bufop(q, fill_user_buffer, vb, pb);
+        if (pb)
+                call_void_bufop(q, fill_user_buffer, vb, pb);
 
         /*
          * If streamon has been called, and we haven't yet called
@@ -1731,7 +1740,8 @@ static void __vb2_dqbuf(struct vb2_buffer *vb)
  * The return values from this function are intended to be directly returned
  * from vidioc_dqbuf handler in driver.
  */
-int vb2_core_dqbuf(struct vb2_queue *q, void *pb, bool nonblocking)
+int vb2_core_dqbuf(struct vb2_queue *q, unsigned int *pindex, void *pb,
+                   bool nonblocking)
 {
         struct vb2_buffer *vb = NULL;
         int ret;
@@ -1754,8 +1764,12 @@ int vb2_core_dqbuf(struct vb2_queue *q, void *pb, bool nonblocking)
 
         call_void_vb_qop(vb, buf_finish, vb);
 
+        if (pindex)
+                *pindex = vb->index;
+
         /* Fill buffer information for the userspace */
-        call_void_bufop(q, fill_user_buffer, vb, pb);
+        if (pb)
+                call_void_bufop(q, fill_user_buffer, vb, pb);
 
         /* Remove from videobuf queue */
         list_del(&vb->queued_entry);
@@ -1828,7 +1842,7 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
          * that's done in dqbuf, but that's not going to happen when we
          * cancel the whole queue. Note: this code belongs here, not in
          * __vb2_dqbuf() since in vb2_internal_dqbuf() there is a critical
-         * call to __fill_v4l2_buffer() after buf_finish(). That order can't
+         * call to __fill_user_buffer() after buf_finish(). That order can't
          * be changed, so we can't move the buf_finish() to __vb2_dqbuf().
          */
         for (i = 0; i < q->num_buffers; ++i) {
@@ -2357,7 +2371,6 @@ struct vb2_fileio_data {
         unsigned int count;
         unsigned int type;
         unsigned int memory;
-        struct vb2_buffer *b;
         struct vb2_fileio_buf bufs[VB2_MAX_FRAME];
         unsigned int cur_index;
         unsigned int initial_index;
@@ -2410,12 +2423,6 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
         if (fileio == NULL)
                 return -ENOMEM;
 
-        fileio->b = kzalloc(q->buf_struct_size, GFP_KERNEL);
-        if (fileio->b == NULL) {
-                kfree(fileio);
-                return -ENOMEM;
-        }
-
         fileio->read_once = q->fileio_read_once;
         fileio->write_immediately = q->fileio_write_immediately;
 
@@ -2460,13 +2467,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
                  * Queue all buffers.
                  */
                 for (i = 0; i < q->num_buffers; i++) {
-                        struct vb2_buffer *b = fileio->b;
-
-                        memset(b, 0, q->buf_struct_size);
-                        b->type = q->type;
-                        b->memory = q->memory;
-                        b->index = i;
-                        ret = vb2_core_qbuf(q, i, b);
+                        ret = vb2_core_qbuf(q, i, NULL);
                         if (ret)
                                 goto err_reqbufs;
                         fileio->bufs[i].queued = 1;
@@ -2511,7 +2512,6 @@ static int __vb2_cleanup_fileio(struct vb2_queue *q)
                 q->fileio = NULL;
                 fileio->count = 0;
                 vb2_core_reqbufs(q, fileio->memory, &fileio->count);
-                kfree(fileio->b);
                 kfree(fileio);
                 dprintk(3, "file io emulator closed\n");
         }
@@ -2539,7 +2539,8 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
          * else is able to provide this information with the write() operation.
          */
         bool copy_timestamp = !read && q->copy_timestamp;
-        int ret, index;
+        unsigned index;
+        int ret;
 
         dprintk(3, "mode %s, offset %ld, count %zd, %sblocking\n",
                 read ? "read" : "write", (long)*ppos, count,
@@ -2564,22 +2565,20 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
          */
         index = fileio->cur_index;
         if (index >= q->num_buffers) {
-                struct vb2_buffer *b = fileio->b;
+                struct vb2_buffer *b;
 
                 /*
                  * Call vb2_dqbuf to get buffer back.
                  */
-                memset(b, 0, q->buf_struct_size);
-                b->type = q->type;
-                b->memory = q->memory;
-                ret = vb2_core_dqbuf(q, b, nonblock);
+                ret = vb2_core_dqbuf(q, &index, NULL, nonblock);
                 dprintk(5, "vb2_dqbuf result: %d\n", ret);
                 if (ret)
                         return ret;
                 fileio->dq_count += 1;
 
-                fileio->cur_index = index = b->index;
+                fileio->cur_index = index;
                 buf = &fileio->bufs[index];
+                b = q->bufs[index];
 
                 /*
                  * Get number of bytes filled by the driver
@@ -2630,7 +2629,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
          * Queue next buffer if required.
          */
         if (buf->pos == buf->size || (!read && fileio->write_immediately)) {
-                struct vb2_buffer *b = fileio->b;
+                struct vb2_buffer *b = q->bufs[index];
 
                 /*
                  * Check if this is the last buffer to read.
@@ -2643,15 +2642,11 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
                 /*
                  * Call vb2_qbuf and give buffer to the driver.
                  */
-                memset(b, 0, q->buf_struct_size);
-                b->type = q->type;
-                b->memory = q->memory;
-                b->index = index;
                 b->planes[0].bytesused = buf->pos;
 
                 if (copy_timestamp)
                         b->timestamp = ktime_get_ns();
-                ret = vb2_core_qbuf(q, index, b);
+                ret = vb2_core_qbuf(q, index, NULL);
                 dprintk(5, "vb2_dbuf result: %d\n", ret);
                 if (ret)
                         return ret;
@@ -2713,10 +2708,9 @@ static int vb2_thread(void *data)
 {
         struct vb2_queue *q = data;
         struct vb2_threadio_data *threadio = q->threadio;
-        struct vb2_fileio_data *fileio = q->fileio;
         bool copy_timestamp = false;
-        int prequeue = 0;
-        int index = 0;
+        unsigned prequeue = 0;
+        unsigned index = 0;
         int ret = 0;
 
         if (q->is_output) {
@@ -2728,37 +2722,34 @@ static int vb2_thread(void *data)
 
         for (;;) {
                 struct vb2_buffer *vb;
-                struct vb2_buffer *b = fileio->b;
 
                 /*
                  * Call vb2_dqbuf to get buffer back.
                  */
-                memset(b, 0, q->buf_struct_size);
-                b->type = q->type;
-                b->memory = q->memory;
                 if (prequeue) {
-                        b->index = index++;
+                        vb = q->bufs[index++];
                         prequeue--;
                 } else {
                         call_void_qop(q, wait_finish, q);
                         if (!threadio->stop)
-                                ret = vb2_core_dqbuf(q, b, 0);
+                                ret = vb2_core_dqbuf(q, &index, NULL, 0);
                         call_void_qop(q, wait_prepare, q);
                         dprintk(5, "file io: vb2_dqbuf result: %d\n", ret);
+                        if (!ret)
+                                vb = q->bufs[index];
                 }
                 if (ret || threadio->stop)
                         break;
                 try_to_freeze();
 
-                vb = q->bufs[b->index];
-                if (b->state == VB2_BUF_STATE_DONE)
+                if (vb->state == VB2_BUF_STATE_DONE)
                         if (threadio->fnc(vb, threadio->priv))
                                 break;
                 call_void_qop(q, wait_finish, q);
                 if (copy_timestamp)
-                        b->timestamp = ktime_get_ns();;
+                        vb->timestamp = ktime_get_ns();;
                 if (!threadio->stop)
-                        ret = vb2_core_qbuf(q, b->index, b);
+                        ret = vb2_core_qbuf(q, vb->index, NULL);
                 call_void_qop(q, wait_prepare, q);
                 if (ret || threadio->stop)
                         break;
diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
index c9a28605511a..91f552124050 100644
--- a/drivers/media/v4l2-core/videobuf2-v4l2.c
+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
@@ -625,7 +625,7 @@ static int vb2_internal_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b,
                 return -EINVAL;
         }
 
-        ret = vb2_core_dqbuf(q, b, nonblocking);
+        ret = vb2_core_dqbuf(q, NULL, b, nonblocking);
 
         return ret;
 }