Re: [PATCH] misc: mic: scif: Fix error handling path

[John Hubbard]

On 9/19/20 7:51 PM, Souptick Joarder wrote:
> Inside __scif_pin_pages(), when map_flags != SCIF_MAP_KERNEL it
> will call pin_user_pages_fast() to map nr_pages. However,
> pin_user_pages_fast() might fail with a return value -ERRNO.
>
> The return value is stored in pinned_pages->nr_pages. which in
> turn is passed to unpin_user_pages(), which expects
> pinned_pages->nr_pages >=0, else disaster.
>
> Fix this by assigning pinned_pages->nr_pages to 0 if
> pin_user_pages_fast() returns -ERRNO.
>
> Fixes:	ba612aa8b487 ("misc: mic: SCIF memory registration and
> unregistration")
> Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---

Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>

thanks,
--
John Hubbard
NVIDIA

>   drivers/misc/mic/scif/scif_rma.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/misc/mic/scif/scif_rma.c b/drivers/misc/mic/scif/scif_rma.c
> index 2da3b47..18fb9d8 100644
> --- a/drivers/misc/mic/scif/scif_rma.c
> +++ b/drivers/misc/mic/scif/scif_rma.c
> @@ -1392,6 +1392,8 @@ int __scif_pin_pages(void *addr, size_t len, int *out_prot,
>   				(prot & SCIF_PROT_WRITE) ? FOLL_WRITE : 0,
>   				pinned_pages->pages);
>   		if (nr_pages != pinned_pages->nr_pages) {
> +			if (pinned_pages->nr_pages < 0)
> +				pinned_pages->nr_pages = 0;
>   			if (try_upgrade) {
>   				if (ulimit)
>   					__scif_dec_pinned_vm_lock(mm, nr_pages);
> @@ -1408,7 +1410,6 @@ int __scif_pin_pages(void *addr, size_t len, int *out_prot,
>   
>   	if (pinned_pages->nr_pages < nr_pages) {
>   		err = -EFAULT;
> -		pinned_pages->nr_pages = nr_pages;
>   		goto dec_pinned;
>   	}
>   
> @@ -1421,7 +1422,6 @@ int __scif_pin_pages(void *addr, size_t len, int *out_prot,
>   		__scif_dec_pinned_vm_lock(mm, nr_pages);
>   	/* Something went wrong! Rollback */
>   error_unmap:
> -	pinned_pages->nr_pages = nr_pages;
>   	scif_destroy_pinned_pages(pinned_pages);
>   	*pages = NULL;
>   	dev_dbg(scif_info.mdev.this_device,