Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755219Ab2FNDS1 (ORCPT ); Wed, 13 Jun 2012 23:18:27 -0400 Received: from mga02.intel.com ([134.134.136.20]:51332 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755021Ab2FNDS0 (ORCPT ); Wed, 13 Jun 2012 23:18:26 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,352,1309762800"; d="scan'208";a="152917163" Subject: Re: [PATCH] DMA: PL330: Fix racy mutex unlock From: Vinod Koul To: Javi Merino Cc: linux-kernel@vger.kernel.org, dan.j.williams@intel.com, Jassi Brar In-Reply-To: <1339596420-18127-1-git-send-email-javi.merino@arm.com> References: <1339596420-18127-1-git-send-email-javi.merino@arm.com> Content-Type: text/plain; charset="UTF-8" Date: Thu, 14 Jun 2012 08:41:06 +0530 Message-ID: <1339643466.1927.1638.camel@vkoul-udesk3> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3496 Lines: 102 On Wed, 2012-06-13 at 15:07 +0100, Javi Merino wrote: > pl330_update() stores a pointer to the thrd->req that finished, which > contains a pointer to the corresponding pl330_req. This is done with > the pl330_lock held. Then, it iterates through the req_done list, > calling the callback for each of the requests that are done. The > problem is that the driver releases the lock before calling the > callback for each of the callbacks. pl330_submit_req() running in > another processor can then acquire the lock and insert another request > in one of the thrd->req that hasn't been processed yet, replacing the > pointer to pl330_req there. When the callback returns in > pl330_update() and the next rqdone is popped from the list, it > dereferences the pl330_req pointer to the just scheduled pl330_req, > instead of the one that has finished, calling pl330 with the wrong r. > > This patch fixes this by storing the pointer to pl330_req directly in > the list. > > Signed-off-by: Javi Merino > Cc: Jassi Brar Applied, thanks > --- > drivers/dma/pl330.c | 26 ++++++++++---------------- > 1 files changed, 10 insertions(+), 16 deletions(-) > > diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c > index cbcc28e..b1d93b0 100644 > --- a/drivers/dma/pl330.c > +++ b/drivers/dma/pl330.c > @@ -392,6 +392,8 @@ struct pl330_req { > struct pl330_reqcfg *cfg; > /* Pointer to first xfer in the request. */ > struct pl330_xfer *x; > + /* Hook to attach to DMAC's list of reqs with due callback */ > + struct list_head rqd; > }; > > /* > @@ -461,8 +463,6 @@ struct _pl330_req { > /* Number of bytes taken to setup MC for the req */ > u32 mc_len; > struct pl330_req *r; > - /* Hook to attach to DMAC's list of reqs with due callback */ > - struct list_head rqd; > }; > > /* ToBeDone for tasklet */ > @@ -1683,7 +1683,7 @@ static void pl330_dotask(unsigned long data) > /* Returns 1 if state was updated, 0 otherwise */ > static int pl330_update(const struct pl330_info *pi) > { > - struct _pl330_req *rqdone; > + struct pl330_req *rqdone, *tmp; > struct pl330_dmac *pl330; > unsigned long flags; > void __iomem *regs; > @@ -1750,7 +1750,10 @@ static int pl330_update(const struct pl330_info *pi) > if (active == -1) /* Aborted */ > continue; > > - rqdone = &thrd->req[active]; > + /* Detach the req */ > + rqdone = thrd->req[active].r; > + thrd->req[active].r = NULL; > + > mark_free(thrd, active); > > /* Get going again ASAP */ > @@ -1762,20 +1765,11 @@ static int pl330_update(const struct pl330_info *pi) > } > > /* Now that we are in no hurry, do the callbacks */ > - while (!list_empty(&pl330->req_done)) { > - struct pl330_req *r; > - > - rqdone = container_of(pl330->req_done.next, > - struct _pl330_req, rqd); > - > - list_del_init(&rqdone->rqd); > - > - /* Detach the req */ > - r = rqdone->r; > - rqdone->r = NULL; > + list_for_each_entry_safe(rqdone, tmp, &pl330->req_done, rqd) { > + list_del(&rqdone->rqd); > > spin_unlock_irqrestore(&pl330->lock, flags); > - _callback(r, PL330_ERR_NONE); > + _callback(rqdone, PL330_ERR_NONE); > spin_lock_irqsave(&pl330->lock, flags); > } > -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/