Re: [PATCH v2] selinux: hooks: use kmalloc() to allocate path buffer

[David Laight <david.laight.linux@gmail.com>]

On Sun, 31 May 2026 18:15:02 +0300
Mike Rapoport <rppt@kernel.org> wrote:

> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> selinux_genfs_get_sid() allocates memory for a path with __get_free_page().
> 
> Such usage does not require a "page" and the size of the buffer should
> actually be PATH_MAX which may be less than PAGE_SIZE on some
> architectures.
> 
> Replace __get_free_page() for allocation of a path buffer with kmalloc()
> and make it explicit that the buffer size is PATH_MAX.
> 
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> v2 changes:
> * explicitly use kmalloc() with PATH_MAX
> 
>  security/selinux/hooks.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 0f704380a8c8..19493198ece1 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1336,11 +1336,11 @@ static int selinux_genfs_get_sid(struct dentry *dentry,
>  	struct super_block *sb = dentry->d_sb;
>  	char *buffer, *path;
>  
> -	buffer = (char *)__get_free_page(GFP_KERNEL);
> +	buffer = kmalloc(GFP_KERNEL, PATH_MAX);

At least get the args in the right order.

>  	if (!buffer)
>  		return -ENOMEM;
>  
> -	path = dentry_path_raw(dentry, buffer, PAGE_SIZE);
> +	path = dentry_path_raw(dentry, buffer, PATH_MAX);
>  	if (IS_ERR(path))
>  		rc = PTR_ERR(path);
>  	else {
> @@ -1361,7 +1361,7 @@ static int selinux_genfs_get_sid(struct dentry *dentry,
>  			rc = 0;
>  		}
>  	}
> -	free_page((unsigned long)buffer);
> +	kfree(buffer);
>  	return rc;
>  }
>