strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with sysfs_emit().

Direct replacement is safe here since its ok for `kernel_param_ops.get()`
to return -errno [3].

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89
[3] https://elixir.bootlin.com/linux/v6.5/source/include/linux/moduleparam.h#L52

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
---
v2:
 * Removes patch [1/2] which replaced module_param_call with module_param_cb.
 * Use sysfs_emit instead of strscpy.

v1:
 * https://lore.kernel.org/all/20230830215426.4181755-1-azeemshaikh38@gmail.com/

 fs/ocfs2/dlmfs/dlmfs.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 81265123ce6c..b38776ba3306 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -80,8 +80,7 @@ static int param_set_dlmfs_capabilities(const char *val,
 static int param_get_dlmfs_capabilities(char *buffer,
 					const struct kernel_param *kp)
 {
-	return strlcpy(buffer, DLMFS_CAPABILITIES,
-		       strlen(DLMFS_CAPABILITIES) + 1);
+	return sysfs_emit(buffer, DLMFS_CAPABILITIES);
 }
 module_param_call(capabilities, param_set_dlmfs_capabilities,
 		  param_get_dlmfs_capabilities, NULL, 0444);
--
2.42.0.283.g2d96d420d3-goog

On 9/1/23 3:38 AM, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with sysfs_emit().
> 
> Direct replacement is safe here since its ok for `kernel_param_ops.get()`
> to return -errno [3].
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> [3] https://elixir.bootlin.com/linux/v6.5/source/include/linux/moduleparam.h#L52
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>

Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>

> ---
> v2:
>  * Removes patch [1/2] which replaced module_param_call with module_param_cb.
>  * Use sysfs_emit instead of strscpy.
> 
> v1:
>  * https://lore.kernel.org/all/20230830215426.4181755-1-azeemshaikh38@gmail.com/
> 
>  fs/ocfs2/dlmfs/dlmfs.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
> index 81265123ce6c..b38776ba3306 100644
> --- a/fs/ocfs2/dlmfs/dlmfs.c
> +++ b/fs/ocfs2/dlmfs/dlmfs.c
> @@ -80,8 +80,7 @@ static int param_set_dlmfs_capabilities(const char *val,
>  static int param_get_dlmfs_capabilities(char *buffer,
>  					const struct kernel_param *kp)
>  {
> -	return strlcpy(buffer, DLMFS_CAPABILITIES,
> -		       strlen(DLMFS_CAPABILITIES) + 1);
> +	return sysfs_emit(buffer, DLMFS_CAPABILITIES);
>  }
>  module_param_call(capabilities, param_set_dlmfs_capabilities,
>  		  param_get_dlmfs_capabilities, NULL, 0444);
> --
> 2.42.0.283.g2d96d420d3-goog
>