RE: [PATCH AUTOSEL 5.4 199/266] misc: xilinx-sdfec: improve get_user_pages_fast() error handling

[Dragan Cvetic <draganc@xilinx.com>]

Hi Sasha,

Thank you for the patch.


> -----Original Message-----
> From: Sasha Levin <sashal@kernel.org>
> Sent: Thursday 18 June 2020 02:15
> To: linux-kernel@vger.kernel.org; stable@vger.kernel.org
> Cc: John Hubbard <jhubbard@nvidia.com>; Derek Kiernan <dkiernan@xilinx.com>; Dragan Cvetic <draganc@xilinx.com>; Arnd
> Bergmann <arnd@arndb.de>; Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Michal Simek <michals@xilinx.com>; linux-arm-
> kernel@lists.infradead.org; Sasha Levin <sashal@kernel.org>
> Subject: [PATCH AUTOSEL 5.4 199/266] misc: xilinx-sdfec: improve get_user_pages_fast() error handling
> 
> From: John Hubbard <jhubbard@nvidia.com>
> 
> [ Upstream commit 57343d51613227373759f5b0f2eede257fd4b82e ]
> 
> This fixes the case of get_user_pages_fast() returning a -errno.
> The result needs to be stored in a signed integer. And for safe
> signed/unsigned comparisons, it's best to keep everything signed.
> And get_user_pages_fast() also expects a signed value for number
> of pages to pin.
> 
> Therefore, change most relevant variables, from u32 to int. Leave
> "n" unsigned, for convenience in checking for overflow. And provide
> a WARN_ON_ONCE() and early return, if overflow occurs.
> 
> Also, as long as we're tidying up: rename the page array from page,
> to pages, in order to match the conventions used in most other call
> sites.
> 
> Fixes: 20ec628e8007e ("misc: xilinx_sdfec: Add ability to configure LDPC")
> Cc: Derek Kiernan <derek.kiernan@xilinx.com>
> Cc: Dragan Cvetic <dragan.cvetic@xilinx.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Michal Simek <michal.simek@xilinx.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> Link: https://lore.kernel.org/r/20200527012628.1100649-2-jhubbard@nvidia.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/misc/xilinx_sdfec.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/misc/xilinx_sdfec.c b/drivers/misc/xilinx_sdfec.c
> index 48ba7e02bed7..d4c14b617201 100644
> --- a/drivers/misc/xilinx_sdfec.c
> +++ b/drivers/misc/xilinx_sdfec.c
> @@ -602,10 +602,10 @@ static int xsdfec_table_write(struct xsdfec_dev *xsdfec, u32 offset,
>  			      const u32 depth)
>  {
>  	u32 reg = 0;
> -	u32 res;
> -	u32 n, i;
> +	int res, i, nr_pages;
> +	u32 n;
>  	u32 *addr = NULL;
> -	struct page *page[MAX_NUM_PAGES];
> +	struct page *pages[MAX_NUM_PAGES];
> 
>  	/*
>  	 * Writes that go beyond the length of
> @@ -622,15 +622,22 @@ static int xsdfec_table_write(struct xsdfec_dev *xsdfec, u32 offset,
>  	if ((len * XSDFEC_REG_WIDTH_JUMP) % PAGE_SIZE)
>  		n += 1;
> 
> -	res = get_user_pages_fast((unsigned long)src_ptr, n, 0, page);
> -	if (res < n) {
> -		for (i = 0; i < res; i++)
> -			put_page(page[i]);
> +	if (WARN_ON_ONCE(n > INT_MAX))
> +		return -EINVAL;
> +
> +	nr_pages = n;
> +
> +	res = get_user_pages_fast((unsigned long)src_ptr, nr_pages, 0, pages);
> +	if (res < nr_pages) {
> +		if (res > 0) {
> +			for (i = 0; i < res; i++)
> +				put_page(pages[i]);
> +		}
>  		return -EINVAL;
>  	}
> 
> -	for (i = 0; i < n; i++) {
> -		addr = kmap(page[i]);
> +	for (i = 0; i < nr_pages; i++) {
> +		addr = kmap(pages[i]);
>  		do {
>  			xsdfec_regwrite(xsdfec,
>  					base_addr + ((offset + reg) *
> @@ -639,7 +646,7 @@ static int xsdfec_table_write(struct xsdfec_dev *xsdfec, u32 offset,
>  			reg++;
>  		} while ((reg < len) &&
>  			 ((reg * XSDFEC_REG_WIDTH_JUMP) % PAGE_SIZE));
> -		put_page(page[i]);
> +		put_page(pages[i]);
>  	}
>  	return reg;
>  }
> --
> 2.25.1

Acked-by: Dragan Cvetic <dragan.cvetic@xilinx.com>

Regards
Dragan