4.4-stable review patch. If anyone has any objections, please let me know.
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From: Greg Hackmann ghackmann@android.com
The ION_IOC_{MAP,SHARE} ioctls drop and reacquire client->lock several times while operating on one of the client's ion_handles. This creates windows where userspace can call ION_IOC_FREE on the same client with the same handle, and effectively make the kernel drop its own reference. For example:
- thread A: ION_IOC_ALLOC creates an ion_handle with refcount 1 - thread A: starts ION_IOC_MAP and increments the refcount to 2 - thread B: ION_IOC_FREE decrements the refcount to 1 - thread B: ION_IOC_FREE decrements the refcount to 0 and frees the handle - thread A: continues ION_IOC_MAP with a dangling ion_handle * to freed memory
Fix this by holding client->lock for the duration of ION_IOC_{MAP,SHARE}, preventing the concurrent ION_IOC_FREE. Also remove ion_handle_get_by_id(), since there's literally no way to use it safely.
This patch is applied on top of 4.4.y, and applies to older kernels too. 4.9.y was fixed separately. Kernels 4.12 and later are unaffected, since all the underlying ion_handle infrastructure has been ripped out.
Cc: stable@vger.kernel.org # v4.4- Signed-off-by: Greg Hackmann ghackmann@google.com Acked-by: Laura Abbott labbott@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- v2: remove Change-Id line from commit message
drivers/staging/android/ion/ion.c | 60 +++++++++++++++++++++++--------------- 1 file changed, 37 insertions(+), 23 deletions(-)
--- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -449,18 +449,6 @@ static struct ion_handle *ion_handle_get return ERR_PTR(-EINVAL); }
-struct ion_handle *ion_handle_get_by_id(struct ion_client *client, - int id) -{ - struct ion_handle *handle; - - mutex_lock(&client->lock); - handle = ion_handle_get_by_id_nolock(client, id); - mutex_unlock(&client->lock); - - return handle; -} - static bool ion_handle_validate(struct ion_client *client, struct ion_handle *handle) { @@ -1138,24 +1126,28 @@ static struct dma_buf_ops dma_buf_ops = .kunmap = ion_dma_buf_kunmap, };
-struct dma_buf *ion_share_dma_buf(struct ion_client *client, - struct ion_handle *handle) +static struct dma_buf *__ion_share_dma_buf(struct ion_client *client, + struct ion_handle *handle, + bool lock_client) { DEFINE_DMA_BUF_EXPORT_INFO(exp_info); struct ion_buffer *buffer; struct dma_buf *dmabuf; bool valid_handle;
- mutex_lock(&client->lock); + if (lock_client) + mutex_lock(&client->lock); valid_handle = ion_handle_validate(client, handle); if (!valid_handle) { WARN(1, "%s: invalid handle passed to share.\n", __func__); - mutex_unlock(&client->lock); + if (lock_client) + mutex_unlock(&client->lock); return ERR_PTR(-EINVAL); } buffer = handle->buffer; ion_buffer_get(buffer); - mutex_unlock(&client->lock); + if (lock_client) + mutex_unlock(&client->lock);
exp_info.ops = &dma_buf_ops; exp_info.size = buffer->size; @@ -1170,14 +1162,21 @@ struct dma_buf *ion_share_dma_buf(struct
return dmabuf; } + +struct dma_buf *ion_share_dma_buf(struct ion_client *client, + struct ion_handle *handle) +{ + return __ion_share_dma_buf(client, handle, true); +} EXPORT_SYMBOL(ion_share_dma_buf);
-int ion_share_dma_buf_fd(struct ion_client *client, struct ion_handle *handle) +static int __ion_share_dma_buf_fd(struct ion_client *client, + struct ion_handle *handle, bool lock_client) { struct dma_buf *dmabuf; int fd;
- dmabuf = ion_share_dma_buf(client, handle); + dmabuf = __ion_share_dma_buf(client, handle, lock_client); if (IS_ERR(dmabuf)) return PTR_ERR(dmabuf);
@@ -1187,8 +1186,19 @@ int ion_share_dma_buf_fd(struct ion_clie
return fd; } + +int ion_share_dma_buf_fd(struct ion_client *client, struct ion_handle *handle) +{ + return __ion_share_dma_buf_fd(client, handle, true); +} EXPORT_SYMBOL(ion_share_dma_buf_fd);
+static int ion_share_dma_buf_fd_nolock(struct ion_client *client, + struct ion_handle *handle) +{ + return __ion_share_dma_buf_fd(client, handle, false); +} + struct ion_handle *ion_import_dma_buf(struct ion_client *client, int fd) { struct dma_buf *dmabuf; @@ -1335,11 +1345,15 @@ static long ion_ioctl(struct file *filp, { struct ion_handle *handle;
- handle = ion_handle_get_by_id(client, data.handle.handle); - if (IS_ERR(handle)) + mutex_lock(&client->lock); + handle = ion_handle_get_by_id_nolock(client, data.handle.handle); + if (IS_ERR(handle)) { + mutex_unlock(&client->lock); return PTR_ERR(handle); - data.fd.fd = ion_share_dma_buf_fd(client, handle); - ion_handle_put(handle); + } + data.fd.fd = ion_share_dma_buf_fd_nolock(client, handle); + ion_handle_put_nolock(handle); + mutex_unlock(&client->lock); if (data.fd.fd < 0) ret = data.fd.fd; break;