linux-kernel - Re: [PATCH] pds_fwctl: Replace kzalloc + copy_from_user with memdup_user in pdsfc_fw

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Message-ID: <fdf330e2-c47d-480f-8a8f-09e73d454d83@amd.com>
Date: Wed, 17 Sep 2025 08:46:14 -0700
From: Brett Creeley <bcreeley@....com>
To: Thorsten Blum <thorsten.blum@...ux.dev>,
 Brett Creeley <brett.creeley@....com>, Dave Jiang <dave.jiang@...el.com>,
 Jason Gunthorpe <jgg@...pe.ca>, Saeed Mahameed <saeedm@...dia.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pds_fwctl: Replace kzalloc + copy_from_user with
 memdup_user in pdsfc_fw_rpc

On 9/17/2025 8:09 AM, Thorsten Blum wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> Replace kzalloc() followed by copy_from_user() with memdup_user() to
> improve and simplify pdsfc_fw_rpc().
> 
> Return early if an error occurs and remove the obsolete 'err_out' label.
> 
> No functional changes intended.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> ---
>   drivers/fwctl/pds/main.c | 16 ++++------------
>   1 file changed, 4 insertions(+), 12 deletions(-)

Thanks for the patch.

Tested-by: Brett Creeley <brett.creeley@....com>

> 
> diff --git a/drivers/fwctl/pds/main.c b/drivers/fwctl/pds/main.c
> index 9b9d1f6b5556..04d84f892fb8 100644
> --- a/drivers/fwctl/pds/main.c
> +++ b/drivers/fwctl/pds/main.c
> @@ -6,6 +6,7 @@
>   #include <linux/pci.h>
>   #include <linux/vmalloc.h>
>   #include <linux/bitfield.h>
> +#include <linux/string.h>
> 
>   #include <uapi/fwctl/fwctl.h>
>   #include <uapi/fwctl/pds.h>
> @@ -366,18 +367,10 @@ static void *pdsfc_fw_rpc(struct fwctl_uctx *uctx, enum fwctl_rpc_scope scope,
>                  return ERR_PTR(err);
> 
>          if (rpc->in.len > 0) {
> -               in_payload = kzalloc(rpc->in.len, GFP_KERNEL);
> -               if (!in_payload) {
> -                       dev_err(dev, "Failed to allocate in_payload\n");
> -                       err = -ENOMEM;
> -                       goto err_out;
> -               }
> -
> -               if (copy_from_user(in_payload, u64_to_user_ptr(rpc->in.payload),
> -                                  rpc->in.len)) {
> +               in_payload = memdup_user(u64_to_user_ptr(rpc->in.payload), rpc->in.len);
> +               if (IS_ERR(in_payload)) {
>                          dev_dbg(dev, "Failed to copy in_payload from user\n");
> -                       err = -EFAULT;
> -                       goto err_in_payload;
> +                       return in_payload;
>                  }
> 
>                  in_payload_dma_addr = dma_map_single(dev->parent, in_payload,
> @@ -453,7 +446,6 @@ static void *pdsfc_fw_rpc(struct fwctl_uctx *uctx, enum fwctl_rpc_scope scope,
>                                   rpc->in.len, DMA_TO_DEVICE);
>   err_in_payload:
>          kfree(in_payload);
> -err_out:
>          if (err)
>                  return ERR_PTR(err);
> 
> --
> 2.51.0
>