From a1ed64efc5f68fc830fea08e96363d4459bb07a6 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Niklas=20S=C3=B6derlund?= Date: Tue, 16 May 2017 01:09:17 +0200 Subject: [PATCH] dmaengine: rcar-dmac: wait for ISR to finish before freeing resources MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This fixes a race condition where the channel resources could be freed before the ISR had finished running resulting in a NULL pointer reference from the ISR. [ 167.148934] Unable to handle kernel NULL pointer dereference at virtual address 00000000 [ 167.157051] pgd = ffff80003c641000 [ 167.160449] [00000000] *pgd=000000007c507003, *pud=000000007c4ff003, *pmd=0000000000000000 [ 167.168719] Internal error: Oops: 96000046 [#1] PREEMPT SMP [ 167.174289] Modules linked in: [ 167.177348] CPU: 3 PID: 10547 Comm: dma_ioctl Not tainted 4.11.0-rc1-00001-g8d92afddc2f6633a #73 [ 167.186131] Hardware name: Renesas Salvator-X board based on r8a7795 (DT) [ 167.192917] task: ffff80003a411a00 task.stack: ffff80003bcd4000 [ 167.198850] PC is at rcar_dmac_chan_prep_sg+0xe0/0x400 [ 167.203985] LR is at rcar_dmac_chan_prep_sg+0x48/0x400 Based of previous work by: Hiroyuki Yokoyama . Signed-off-by: Niklas Söderlund Signed-off-by: Vinod Koul --- drivers/dma/sh/rcar-dmac.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c index fb07cd5..d2cb4a0 100644 --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -1010,7 +1010,11 @@ static void rcar_dmac_free_chan_resources(struct dma_chan *chan) rcar_dmac_chan_halt(rchan); spin_unlock_irq(&rchan->lock); - /* Now no new interrupts will occur */ + /* + * Now no new interrupts will occur, but one might already be + * running. Wait for it to finish before freeing resources. + */ + synchronize_irq(rchan->irq); if (rchan->mid_rid >= 0) { /* The caller is holding dma_list_mutex */ -- 2.7.4