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

From: Sangwoo
Date: Mon Oct 05 2015 - 02:01:21 EST


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 <sangwoo2.park@xxxxxxx>
---
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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