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

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

[Mike Rapoport (Microsoft)]

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.

Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
This is a (tiny) part of larger work of replacing page allocator calls
with kmalloc:

Also in git:
https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/security
---
v4 changes:
* rebase on v7.2-rc1

v3: https://lore.kernel.org/all/20260531165852.1478916-1-rppt@kernel.org
* get the args in the right order

v2: https://lore.kernel.org/all/20260531151502.1467515-1-rppt@kernel.org
* 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 1a713d96206f..d1f089917a82 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(PATH_MAX, GFP_KERNEL);
 	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;
 }
 

---
base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
change-id: 20260520-security-6cdd60da7129

Best regards,
--  
Sincerely yours,
Mike.

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

[Mike Rapoport]

Should have been:

Subject: [PATCH v4] selinux: hooks: use kmalloc() to allocate path buffer

On Tue, Jun 30, 2026 at 01:15:24PM +0300, Mike Rapoport (Microsoft) wrote:
> 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.
> 
> Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> This is a (tiny) part of larger work of replacing page allocator calls
> with kmalloc:
> 
> Also in git:
> https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/security
> ---
> v4 changes:
> * rebase on v7.2-rc1
> 
> v3: https://lore.kernel.org/all/20260531165852.1478916-1-rppt@kernel.org
> * get the args in the right order
> 
> v2: https://lore.kernel.org/all/20260531151502.1467515-1-rppt@kernel.org
> * 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 1a713d96206f..d1f089917a82 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(PATH_MAX, GFP_KERNEL);
>  	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;
>  }
>  
> 
> ---
> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
> change-id: 20260520-security-6cdd60da7129
> 
> Best regards,
> --  
> Sincerely yours,
> Mike.
> 

-- 
Sincerely yours,
Mike.