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SubjectRe: [linux-next PATCH] rapidio: Fix error handling path
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On 9/15/20 8:42 PM, Souptick Joarder wrote:
> There is an error when pin_user_pages_fast() returns -ERRNO and
> inside error handling path driver end up calling unpin_user_pages()
> with -ERRNO which is not correct.
> > This patch will fix the problem.

How about:

rio_dma_transfer() attempts to clamp the return value of
pin_user_pages_fast() to be >= 0. However, the attempt fails because
nr_pages is overridden a few lines later, and restored to the
undesirable -ERRNO value.

The return value is ultimately stored in nr_pages, which in turn is
passed to unpin_user_pages(), which expects nr_pages >= 0, else,
disaster.

Fix this by fixing the nesting of the assignment to nr_pages: nr_pages
should be clamped to zero if pin_user_pages_fast() returns -ERRNO, or
set to the return value of pin_user_pages_fast(), otherwise.

>
> Fixes: e8de370188d09 ("rapidio: add mport char device driver")
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Matthew Wilcox <willy@infradead.org>
> ---
> drivers/rapidio/devices/rio_mport_cdev.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
> index a303429..163b6c72 100644
> --- a/drivers/rapidio/devices/rio_mport_cdev.c
> +++ b/drivers/rapidio/devices/rio_mport_cdev.c
> @@ -871,15 +871,16 @@ static int do_dma_request(struct mport_dma_req *req,
> rmcd_error("pin_user_pages_fast err=%ld",
> pinned);
> nr_pages = 0;
> - } else
> + } else {
> rmcd_error("pinned %ld out of %ld pages",
> pinned, nr_pages);
> + /*
> + * Set nr_pages up to mean "how many pages to unpin, in
> + * the error handler:
> + */
> + nr_pages = pinned;
> + }
> ret = -EFAULT;
> - /*
> - * Set nr_pages up to mean "how many pages to unpin, in
> - * the error handler:
> - */
> - nr_pages = pinned;
> goto err_pg;
> }
>
>

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
--
John Hubbard
NVIDIA

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