| Message ID | 20231204014455.2444734-1-chentao@kylinos.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v3,iwl-next] i40e: Use correct buffer size in i40e_dbg_command_read | expand |
From: Kunwu Chan <chentao@kylinos.cn> 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 <chentao@kylinos.cn> > Suggested-by: Simon Horman <horms@kernel.org> > Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com> > --- > 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
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.
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);
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 <chentao@kylinos.cn> Suggested-by: Simon Horman <horms@kernel.org> Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com> --- 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(-)