Re: [PATCH] security: selinux: Use a kmem_cache for allocation struct file_security_struct

[Stephen Smalley]

On 10/05/2015 01:45 AM, Sangwoo wrote:
> The size of struct file_security_struct is 16byte at my setup.
> But, the real allocation size for per each file_security_struct
> is 64bytes in my setup that kmalloc min size is 64bytes
> because ARCH_DMA_MINALIGN is 64.
> 
> This allocation is called every times at file allocation(alloc_file()).
> So, the total slack memory size(allocated size - request size)
> is increased exponentially.
> 
> E.g) Min Kmalloc Size : 64bytes, Unit : bytes
>   Allocated Size | Request Size | Slack Size | Allocation Count
> ---
>  770048  |192512|   577536   |  12032
> 
> At the result, this change reduce memory usage 42bytes per each
> file_security_struct
> 
> Signed-off-by: Sangwoo 

Acked-by:  Stephen Smalley 

> ---
>  security/selinux/hooks.c |8 ++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 3f8d567..c20e082 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -126,6 +126,7 @@ int selinux_enabled = 1;
>  #endif
>  
>  static struct kmem_cache *sel_inode_cache;
> +static struct kmem_cache *file_security_cache;
>  
>  /**
>   * selinux_secmark_enabled - Check to see if SECMARK is currently enabled
> @@ -287,7 +288,7 @@ static int file_alloc_security(struct file *file)
>   struct file_security_struct *fsec;
>   u32 sid = current_sid();
>  
> - fsec = kzalloc(sizeof(struct file_security_struct), GFP_KERNEL);
> + fsec = kmem_cache_zalloc(file_security_cache, GFP_KERNEL);
>   if (!fsec)
>   return -ENOMEM;
>  
> @@ -302,7 +303,7 @@ static void file_free_security(struct file *file)
>  {
>   struct file_security_struct *fsec = file->f_security;
>   file->f_security = NULL;
> - kfree(fsec);
> + kmem_cache_free(file_security_cache, fsec);
>  }
>  
>  static int superblock_alloc_security(struct super_block *sb)
> @@ -6086,6 +6087,9 @@ static __init int selinux_init(void)
>   sel_inode_cache = kmem_cache_create("selinux_inode_security",
>   sizeof(struct 
> inode_security_struct),
>   0, SLAB_PANIC, NULL);
> + file_security_cache = kmem_cache_create("selinux_file_security",
> + sizeof(struct file_security_struct),
> + 0, SLAB_PANIC, NULL);
>   avc_init();
>  
>   security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks));
> 

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[PATCH] security: selinux: Use a kmem_cache for allocation struct file_security_struct

[Sangwoo]

The size of struct file_security_struct is 16byte at my setup.
But, the real allocation size for per each file_security_struct
is 64bytes in my setup that kmalloc min size is 64bytes
because ARCH_DMA_MINALIGN is 64.

This allocation is called every times at file allocation(alloc_file()).
So, the total slack memory size(allocated size - request size)
is increased exponentially.

E.g) Min Kmalloc Size : 64bytes, Unit : bytes
  Allocated Size | Request Size | Slack Size | Allocation Count
---
 770048  |192512|   577536   |  12032

At the result, this change reduce memory usage 42bytes per each
file_security_struct

Signed-off-by: Sangwoo 
---
 security/selinux/hooks.c |8 ++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3f8d567..c20e082 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -126,6 +126,7 @@ int selinux_enabled = 1;
 #endif
 
 static struct kmem_cache *sel_inode_cache;
+static struct kmem_cache *file_security_cache;
 
 /**
  * selinux_secmark_enabled - Check to see if SECMARK is currently enabled
@@ -287,7 +288,7 @@ static int file_alloc_security(struct file *file)
struct file_security_struct *fsec;
u32 sid = current_sid();
 
-   fsec = kzalloc(sizeof(struct file_security_struct), GFP_KERNEL);
+   fsec = kmem_cache_zalloc(file_security_cache, GFP_KERNEL);
if (!fsec)
return -ENOMEM;
 
@@ -302,7 +303,7 @@ static void file_free_security(struct file *file)
 {
struct file_security_struct *fsec = file->f_security;
file->f_security = NULL;
-   kfree(fsec);
+   kmem_cache_free(file_security_cache, fsec);
 }
 
 static int superblock_alloc_security(struct super_block *sb)
@@ -6086,6 +6087,9 @@ static __init int selinux_init(void)
sel_inode_cache = kmem_cache_create("selinux_inode_security",
sizeof(struct 
inode_security_struct),
0, SLAB_PANIC, NULL);
+   file_security_cache = kmem_cache_create("selinux_file_security",
+   sizeof(struct file_security_struct),
+   0, SLAB_PANIC, NULL);
avc_init();
 
security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks));
-- 
1.7.9.5

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