From 3eaeaee3a2916299e63e8617bba65966753c9cd1 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 12 Aug 2019 16:42:47 +0100 Subject: [PATCH] dma-buf/sw_sync: Synchronize signal vs syncpt free MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit During release of the syncpt, we remove it from the list of syncpt and the tree, but only if it is not already been removed. However, during signaling, we first remove the syncpt from the list. So, if we concurrently free and signal the syncpt, the free may decide that it is not part of the tree and immediately free itself -- meanwhile the signaler goes on to use the now freed datastructure. In particular, we get struck by commit 40c06375e72c ("dma-buf: make dma_fence structure a bit smaller v2") as the cb_list is immediately clobbered by the kfree_rcu. v2: Avoid calling into timeline_fence_release() from under the spinlock Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111381 Fixes: 93db7326a4f9 ("dma-buf/sw-sync: Fix locking around sync_timeline lists") References: 40c06375e72c ("dma-buf: make dma_fence structure a bit smaller v2") Signed-off-by: Chris Wilson Cc: Sumit Semwal Cc: Sean Paul Cc: Gustavo Padovan Cc: Christian König Cc: # v4.14+ Acked-by: Christian König Link: https://patchwork.freedesktop.org/patch/msgid/20190812154247.20508-1-chris@chris-wilson.co.uk --- drivers/dma-buf/sw_sync.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c index 051f6c2873c7a..6713cfb1995c6 100644 --- a/drivers/dma-buf/sw_sync.c +++ b/drivers/dma-buf/sw_sync.c @@ -132,17 +132,14 @@ static void timeline_fence_release(struct dma_fence *fence) { struct sync_pt *pt = dma_fence_to_sync_pt(fence); struct sync_timeline *parent = dma_fence_parent(fence); + unsigned long flags; + spin_lock_irqsave(fence->lock, flags); if (!list_empty(&pt->link)) { - unsigned long flags; - - spin_lock_irqsave(fence->lock, flags); - if (!list_empty(&pt->link)) { - list_del(&pt->link); - rb_erase(&pt->node, &parent->pt_tree); - } - spin_unlock_irqrestore(fence->lock, flags); + list_del(&pt->link); + rb_erase(&pt->node, &parent->pt_tree); } + spin_unlock_irqrestore(fence->lock, flags); sync_timeline_put(parent); dma_fence_free(fence); @@ -265,7 +262,8 @@ static struct sync_pt *sync_pt_create(struct sync_timeline *obj, p = &parent->rb_left; } else { if (dma_fence_get_rcu(&other->base)) { - dma_fence_put(&pt->base); + sync_timeline_put(obj); + kfree(pt); pt = other; goto unlock; } -- 2.39.5