2023-12-04 01:45:55

by Kunwu Chan

[permalink] [raw]
Subject: [PATCH v3 iwl-next] i40e: Use correct buffer size in i40e_dbg_command_read

The size of "i40e_dbg_command_buf" is 256, the size of "name"
depends on "IFNAMSIZ", plus a null character and format size,
the total size is more than 256.

Improve readability and maintainability by replacing a hardcoded string
allocation and formatting by the use of the kasprintf() helper.

Fixes: 02e9c290814c ("i40e: debugfs interface")
Signed-off-by: Kunwu Chan <[email protected]>
Suggested-by: Simon Horman <[email protected]>
Suggested-by: Alexander Lobakin <[email protected]>
---
v2
- Update the size calculation with IFNAMSIZ and sizeof(i40e_dbg_command_buf)
v3
- Use kasprintf to improve readability and maintainability
---
drivers/net/ethernet/intel/i40e/i40e_debugfs.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
index 88240571721a..a176de89de9c 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
@@ -72,23 +72,22 @@ static ssize_t i40e_dbg_command_read(struct file *filp, char __user *buffer,
{
struct i40e_pf *pf = filp->private_data;
int bytes_not_copied;
- int buf_size = 256;
- char *buf;
+ char *buf = NULL;
int len;

/* don't allow partial reads */
if (*ppos != 0)
return 0;
- if (count < buf_size)
- return -ENOSPC;

- buf = kzalloc(buf_size, GFP_KERNEL);
+ buf = kasprintf(GFP_KERNEL, "%s: %s\n",
+ pf->vsi[pf->lan_vsi]->netdev->name,
+ i40e_dbg_command_buf);
if (!buf)
return -ENOSPC;

- len = snprintf(buf, buf_size, "%s: %s\n",
- pf->vsi[pf->lan_vsi]->netdev->name,
- i40e_dbg_command_buf);
+ len = strlen(buf);
+ if (count < len)
+ return -ENOSPC;

bytes_not_copied = copy_to_user(buffer, buf, len);
kfree(buf);
--
2.34.1


2023-12-04 12:52:46

by Alexander Lobakin

[permalink] [raw]
Subject: Re: [PATCH v3 iwl-next] i40e: Use correct buffer size in i40e_dbg_command_read

From: Kunwu Chan <[email protected]>
Date: Mon, 4 Dec 2023 09:44:55 +0800

> The size of "i40e_dbg_command_buf" is 256, the size of "name"
> depends on "IFNAMSIZ", plus a null character and format size,
> the total size is more than 256.
>
> Improve readability and maintainability by replacing a hardcoded string
> allocation and formatting by the use of the kasprintf() helper.
>
> Fixes: 02e9c290814c ("i40e: debugfs interface")
> Signed-off-by: Kunwu Chan <[email protected]>
> Suggested-by: Simon Horman <[email protected]>
> Suggested-by: Alexander Lobakin <[email protected]>
> ---
> v2
> - Update the size calculation with IFNAMSIZ and sizeof(i40e_dbg_command_buf)
> v3
> - Use kasprintf to improve readability and maintainability
> ---
> drivers/net/ethernet/intel/i40e/i40e_debugfs.c | 15 +++++++--------
> 1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> index 88240571721a..a176de89de9c 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_debugfs.c
> @@ -72,23 +72,22 @@ static ssize_t i40e_dbg_command_read(struct file *filp, char __user *buffer,
> {
> struct i40e_pf *pf = filp->private_data;
> int bytes_not_copied;
> - int buf_size = 256;
> - char *buf;
> + char *buf = NULL;

This is unneeded.

> int len;
>
> /* don't allow partial reads */
> if (*ppos != 0)
> return 0;
> - if (count < buf_size)
> - return -ENOSPC;
>
> - buf = kzalloc(buf_size, GFP_KERNEL);
> + buf = kasprintf(GFP_KERNEL, "%s: %s\n",
> + pf->vsi[pf->lan_vsi]->netdev->name,
> + i40e_dbg_command_buf);
> if (!buf)
> return -ENOSPC;
>
> - len = snprintf(buf, buf_size, "%s: %s\n",
> - pf->vsi[pf->lan_vsi]->netdev->name,
> - i40e_dbg_command_buf);
> + len = strlen(buf);

strlen() doesn't include the terminating '\0', but you need to copy it
as well. Hence `strlen(buf) + 1`.

> + if (count < len)
> + return -ENOSPC;

Here you have memory leak in case the condition is true.

>
> bytes_not_copied = copy_to_user(buffer, buf, len);
> kfree(buf);

Taking the above two into account, I'd suggest doing something like:

if (!buf)
return -ENOSPC;

len = strlen(buf) + 1;

if (count < len)
bytes_not_copied = -ENOSPC;
elseif (copy_to_user(buffer, buf, len))
bytes_not_copied = -EFAULT;
else
bytes_not_copied = 0;

kfree(buf);

if (bytes_not_copied)
return bytes_not_copied;

*ppos = len;

return len;
}

Thanks,
Olek

2023-12-05 03:06:09

by Kunwu Chan

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Subject: Re: [PATCH v3 iwl-next] i40e: Use correct buffer size in i40e_dbg_command_read

Hi Alexander,
Thanks for your reply.

It's my bad, I'll follow your suggestion in v4 patch:
1. keep 'buf' as it defined before.
2. resolve memory leak as your suggestion.
3. make 'bytes_not_copied' as a return value for error path.

Thanks again,
Kunwu
On 2023/12/4 20:51, Alexander Lobakin wrote:
> This is unneeded.