From: Andrew Morton <akpm@linux-foundation.org>
To: John Hubbard <jhubbard@nvidia.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Matt Porter <mporter@kernel.crashing.org>,
Alexandre Bounine <alex.bou9@gmail.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
Dan Carpenter <dan.carpenter@oracle.com>,
<linux-media@vger.kernel.org>, <stable@vger.kernel.org>
Subject: Re: [PATCH 1/2] rapidio: fix an error in get_user_pages_fast() error handling
Date: Mon, 18 May 2020 14:37:23 -0700 [thread overview]
Message-ID: <20200518143723.2c3159ddd53345b9cde5d869@linux-foundation.org> (raw)
In-Reply-To: <20200517235620.205225-2-jhubbard@nvidia.com>
On Sun, 17 May 2020 16:56:19 -0700 John Hubbard <jhubbard@nvidia.com> wrote:
> In the case of get_user_pages_fast() returning fewer pages than
> requested, rio_dma_transfer() does not quite do the right thing.
> It attempts to release all the pages that were requested, rather
> than just the pages that were pinned.
>
> Fix the error handling so that only the pages that were successfully
> pinned are released.
>
> ...
>
> --- a/drivers/rapidio/devices/rio_mport_cdev.c
> +++ b/drivers/rapidio/devices/rio_mport_cdev.c
> @@ -877,6 +877,11 @@ rio_dma_transfer(struct file *filp, u32 transfer_mode,
> rmcd_error("pinned %ld out of %ld pages",
> pinned, nr_pages);
> ret = -EFAULT;
> + /*
> + * Set nr_pages up to mean "how many pages to unpin, in
> + * the error handler:
> + */
> + nr_pages = pinned;
> goto err_pg;
> }
The code is a bit odd. If (xfer->loc_addr == 0) then we do the `else'
stuff then fall through to
err_pg:
if (!req->page_list) {
for (i = 0; i < nr_pages; i++)
put_page(page_list[i]);
kfree(page_list);
}
all of which is a big no-op because nr_pages==0 and page_list==NULL,
but it could all be easily avoided.
Oh well. Reviewed-by:me.
next prev parent reply other threads:[~2020-05-18 21:37 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-17 23:56 [PATCH 0/2] rapidio: convert to pin_user_pages(), plus a small fix John Hubbard
2020-05-17 23:56 ` [PATCH 1/2] rapidio: fix an error in get_user_pages_fast() error handling John Hubbard
2020-05-18 21:37 ` Andrew Morton [this message]
2020-05-17 23:56 ` [PATCH 2/2] rapidio: convert get_user_pages() --> pin_user_pages() John Hubbard
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