device_cgroup: Refactor devcgroup_seq_show to use seq_put* helpers

Replace set_access(), set_majmin(), and type_to_char() with new helpers
seq_putaccess(), seq_puttype(), and seq_putversion() that write directly
to 'seq_file'.

Simplify devcgroup_seq_show() by hard-coding "a *:* rwm", and use the
new seq_put* helper functions to list the exceptions otherwise.

This allows us to remove the intermediate string buffers while
maintaining the same functionality, including wildcard handling.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index dc4df7475081cd8993892c74ba72b9da1acf6ae0..7fec575d32d6f115c07a5e89449e52a9fc7e927a 100644 (file)
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -244,45 +244,40 @@ static void devcgroup_css_free(struct cgroup_subsys_state *css)
 #define DEVCG_DENY 2
 #define DEVCG_LIST 3
 
-#define MAJMINLEN 13
-#define ACCLEN 4
-
-static void set_access(char *acc, short access)
+static void seq_putaccess(struct seq_file *m, short access)
 {
-       int idx = 0;
-       memset(acc, 0, ACCLEN);
        if (access & DEVCG_ACC_READ)
-               acc[idx++] = 'r';
+               seq_putc(m, 'r');
        if (access & DEVCG_ACC_WRITE)
-               acc[idx++] = 'w';
+               seq_putc(m, 'w');
        if (access & DEVCG_ACC_MKNOD)
-               acc[idx++] = 'm';
+               seq_putc(m, 'm');
 }
 
-static char type_to_char(short type)
+static void seq_puttype(struct seq_file *m, short type)
 {
        if (type == DEVCG_DEV_ALL)
-               return 'a';
-       if (type == DEVCG_DEV_CHAR)
-               return 'c';
-       if (type == DEVCG_DEV_BLOCK)
-               return 'b';
-       return 'X';
+               seq_putc(m, 'a');
+       else if (type == DEVCG_DEV_CHAR)
+               seq_putc(m, 'c');
+       else if (type == DEVCG_DEV_BLOCK)
+               seq_putc(m, 'b');
+       else
+               seq_putc(m, 'X');
 }
 
-static void set_majmin(char *str, unsigned m)
+static void seq_putversion(struct seq_file *m, unsigned int version)
 {
-       if (m == ~0)
-               strcpy(str, "*");
+       if (version == ~0)
+               seq_putc(m, '*');
        else
-               sprintf(str, "%u", m);
+               seq_printf(m, "%u", version);
 }
 
 static int devcgroup_seq_show(struct seq_file *m, void *v)
 {
        struct dev_cgroup *devcgroup = css_to_devcgroup(seq_css(m));
        struct dev_exception_item *ex;
-       char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN];
 
        rcu_read_lock();
        /*
@@ -292,18 +287,17 @@ static int devcgroup_seq_show(struct seq_file *m, void *v)
         * This way, the file remains as a "whitelist of devices"
         */
        if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
-               set_access(acc, DEVCG_ACC_MASK);
-               set_majmin(maj, ~0);
-               set_majmin(min, ~0);
-               seq_printf(m, "%c %s:%s %s\n", type_to_char(DEVCG_DEV_ALL),
-                          maj, min, acc);
+               seq_puts(m, "a *:* rwm\n");
        } else {
                list_for_each_entry_rcu(ex, &devcgroup->exceptions, list) {
-                       set_access(acc, ex->access);
-                       set_majmin(maj, ex->major);
-                       set_majmin(min, ex->minor);
-                       seq_printf(m, "%c %s:%s %s\n", type_to_char(ex->type),
-                                  maj, min, acc);
+                       seq_puttype(m, ex->type);
+                       seq_putc(m, ' ');
+                       seq_putversion(m, ex->major);
+                       seq_putc(m, ':');
+                       seq_putversion(m, ex->minor);
+                       seq_putc(m, ' ');
+                       seq_putaccess(m, ex->access);
+                       seq_putc(m, '\n');
                }
        }
        rcu_read_unlock();