apparmor: add per cpu work buffers to avoid allocating buffers at every hook

Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/include/path.h

@@ -29,4 +29,57 @@ enum path_flags {
 int aa_path_name(const struct path *path, int flags, char **buffer,
 		 const char **name, const char **info);
 
+#define MAX_PATH_BUFFERS 2
+
+/* Per cpu buffers used during mediation */
+/* preallocated buffers to use during path lookups */
+struct aa_buffers {
+	char *buf[MAX_PATH_BUFFERS];
+};
+
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+
+DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
+
+#define COUNT_ARGS(X...) COUNT_ARGS_HELPER(, ##X, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
+#define COUNT_ARGS_HELPER(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, n, X...) n
+#define CONCAT(X, Y) X ## Y
+#define CONCAT_AFTER(X, Y) CONCAT(X, Y)
+
+#define ASSIGN(FN, X, N) ((X) = FN(N))
+#define EVAL1(FN, X) ASSIGN(FN, X, 0) /*X = FN(0)*/
+#define EVAL2(FN, X, Y...) do { ASSIGN(FN, X, 1);  EVAL1(FN, Y); } while (0)
+#define EVAL(FN, X...) CONCAT_AFTER(EVAL, COUNT_ARGS(X))(FN, X)
+
+#define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
+
+#ifdef CONFIG_DEBUG_PREEMPT
+#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
+#else
+#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
+#endif
+
+#define __get_buffer(N) ({					\
+	struct aa_buffers *__cpu_var; \
+	AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled");  \
+	__cpu_var = this_cpu_ptr(&aa_buffers);			\
+	__cpu_var->buf[(N)]; })
+
+#define __get_buffers(X...)    EVAL(__get_buffer, X)
+
+#define __put_buffers(X, Y...) ((void)&(X))
+
+#define get_buffers(X...)	\
+do {				\
+	preempt_disable();	\
+	__get_buffers(X);	\
+} while (0)
+
+#define put_buffers(X, Y...)	\
+do {				\
+	__put_buffers(X, Y);	\
+	preempt_enable();	\
+} while (0)
+
 #endif /* __AA_PATH_H */

security/apparmor/lsm.c

@@ -41,6 +41,9 @@
 /* Flag indicating whether initialization completed */
 int apparmor_initialized __initdata;
 
+DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
+
+
 /*
  * LSM hook functions
  */
@@ -868,6 +871,43 @@ static int __init set_init_ctx(void)
 	return 0;
 }
 
+static void destroy_buffers(void)
+{
+	u32 i, j;
+
+	for_each_possible_cpu(i) {
+		for_each_cpu_buffer(j) {
+			kfree(per_cpu(aa_buffers, i).buf[j]);
+			per_cpu(aa_buffers, i).buf[j] = NULL;
+		}
+	}
+}
+
+static int __init alloc_buffers(void)
+{
+	u32 i, j;
+
+	for_each_possible_cpu(i) {
+		for_each_cpu_buffer(j) {
+			char *buffer;
+
+			if (cpu_to_node(i) > num_online_nodes())
+				/* fallback to kmalloc for offline nodes */
+				buffer = kmalloc(aa_g_path_max, GFP_KERNEL);
+			else
+				buffer = kmalloc_node(aa_g_path_max, GFP_KERNEL,
+						      cpu_to_node(i));
+			if (!buffer) {
+				destroy_buffers();
+				return -ENOMEM;
+			}
+			per_cpu(aa_buffers, i).buf[j] = buffer;
+		}
+	}
+
+	return 0;
+}
+
 #ifdef CONFIG_SYSCTL
 static int apparmor_dointvec(struct ctl_table *table, int write,
 			     void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -937,11 +977,17 @@ static int __init apparmor_init(void)
 
 	}
 
+	error = alloc_buffers();
+	if (error) {
+		AA_ERROR("Unable to allocate work buffers\n");
+		goto buffers_out;
+	}
+
 	error = set_init_ctx();
 	if (error) {
 		AA_ERROR("Failed to set context on init task\n");
 		aa_free_root_ns();
-		goto alloc_out;
+		goto buffers_out;
 	}
 	security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks));
 
@@ -956,6 +1002,9 @@ static int __init apparmor_init(void)
 
 	return error;
 
+buffers_out:
+	destroy_buffers();
+
 alloc_out:
 	aa_destroy_aafs();
 	aa_teardown_dfa_engine();