From 40af9bab21188d5c0540c5f297b3d4d1643a1c5b 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 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: 8614eada87b4 ("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 --- 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 a0802de8c3a1d..6f5afab7c1a1b 100644 --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -248,10 +248,10 @@ 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); } -- 2.39.5