From: Vinod Koul <vkoul@kernel.org>
To: Pan Bian <bianpan2016@163.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
Maxime Ripard <mripard@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dmaengine: sun6i: Fix use after free
Date: Thu, 14 Nov 2019 12:15:31 +0530 [thread overview]
Message-ID: <20191114064514.GO952516@vkoul-mobl> (raw)
In-Reply-To: <1573126013-17609-1-git-send-email-bianpan2016@163.com>
On 07-11-19, 19:26, Pan Bian wrote:
> The members in the LLI list is released in an incorrect way. Read and
> store the next member before releasing it to avoid accessing the freed
> memory.
>
> Fixes: a90e173f3faf ("dmaengine: sun6i: Add cyclic capability")
>
> Signed-off-by: Pan Bian <bianpan2016@163.com>
> ---
> drivers/dma/sun6i-dma.c | 20 ++++++++++++++------
> 1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index 06cd7f867f7c..096aad7e75bb 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -687,7 +687,7 @@ static struct dma_async_tx_descriptor *sun6i_dma_prep_slave_sg(
> struct sun6i_dma_dev *sdev = to_sun6i_dma_dev(chan->device);
> struct sun6i_vchan *vchan = to_sun6i_vchan(chan);
> struct dma_slave_config *sconfig = &vchan->cfg;
> - struct sun6i_dma_lli *v_lli, *prev = NULL;
> + struct sun6i_dma_lli *v_lli, *next, *prev = NULL;
> struct sun6i_desc *txd;
> struct scatterlist *sg;
> dma_addr_t p_lli;
> @@ -752,8 +752,12 @@ static struct dma_async_tx_descriptor *sun6i_dma_prep_slave_sg(
> return vchan_tx_prep(&vchan->vc, &txd->vd, flags);
>
> err_lli_free:
> - for (prev = txd->v_lli; prev; prev = prev->v_lli_next)
> - dma_pool_free(sdev->pool, prev, virt_to_phys(prev));
> + v_lli = txd->v_lli;
> + while (v_lli) {
> + next = v_lli->v_lli_next;
> + dma_pool_free(sdev->pool, v_lli, virt_to_phys(v_lli));
> + v_lli = next;
Have you seen this issue, a panic trace? Has some static checker flagged
this?
I see the code *seems* equivalent. The prev is assigned to txd->v_lli,
checked and then code block will be executed and updated. When do you
see the case when we access freed memory?
--
~Vinod
prev parent reply other threads:[~2019-11-14 6:45 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-07 11:26 [PATCH] dmaengine: sun6i: Fix use after free Pan Bian
2019-11-14 6:45 ` Vinod Koul [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191114064514.GO952516@vkoul-mobl \
--to=vkoul@kernel.org \
--cc=bianpan2016@163.com \
--cc=dan.j.williams@intel.com \
--cc=dmaengine@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mripard@kernel.org \
--cc=wens@csie.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).