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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>
This commit is contained in:
Thorsten Blum 2025-10-31 22:39:14 +01:00 committed by Paul Moore
parent dfa024bc3f
commit 0e6ebf8778
1 changed files with 25 additions and 31 deletions
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56
security/device_cgroup.c
View File

@ -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();