From a0fe1581a2963e5de0a7389498c5a8d046d4d0f5 Mon Sep 17 00:00:00 2001 From: Liam Mark Date: Fri, 18 Jan 2019 10:37:44 -0800 Subject: [PATCH] staging: android: ion: Support cpu access during dma_buf_detach [ Upstream commit 31eb79db420a3f94c4c45a8c0a05cd30e333f981 ] Often userspace doesn't know when the kernel will be calling dma_buf_detach on the buffer. If userpace starts its CPU access at the same time as the sg list is being freed it could end up accessing the sg list after it has been freed. Thread A Thread B - DMA_BUF_IOCTL_SYNC IOCT - ion_dma_buf_begin_cpu_access - list_for_each_entry - ion_dma_buf_detatch - free_duped_table - dma_sync_sg_for_cpu Fix this by getting the ion_buffer lock before freeing the sg table memory. Fixes: 2a55e7b5e544 ("staging: android: ion: Call dma_map_sg for syncing and mapping") Signed-off-by: Liam Mark Acked-by: Laura Abbott Acked-by: Andrew F. Davis Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/staging/android/ion/ion.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c index 24cb666c9224..dd96ca61a515 100644 --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -257,10 +257,10 @@ static void ion_dma_buf_detatch(struct dma_buf *dmabuf, struct ion_dma_buf_attachment *a = attachment->priv; struct ion_buffer *buffer = dmabuf->priv; - free_duped_table(a->table); mutex_lock(&buffer->lock); list_del(&a->list); mutex_unlock(&buffer->lock); + free_duped_table(a->table); kfree(a); }