[PATCH] replace cad_pid by a struct pid
There are a few places in the kernel where the init task is signaled. The
ctrl+alt+del sequence is one them. It kills a task, usually init, using a
cached pid (cad_pid).
This patch replaces the pid_t by a struct pid to avoid pid wrap around
problem. The struct pid is initialized at boot time in init() and can be
modified through systctl with
/proc/sys/kernel/cad_pid
[ I haven't found any distro using it ? ]
It also introduces a small helper routine kill_cad_pid() which is used
where it seemed ok to use cad_pid instead of pid 1.
[akpm@osdl.org: cleanups, build fix]
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/mips/sgi-ip22/ip22-reset.c b/arch/mips/sgi-ip22/ip22-reset.c
index 8134220..7a941ec 100644
--- a/arch/mips/sgi-ip22/ip22-reset.c
+++ b/arch/mips/sgi-ip22/ip22-reset.c
@@ -123,7 +123,8 @@
if (machine_state & MACHINE_PANICED)
return;
- if ((machine_state & MACHINE_SHUTTING_DOWN) || kill_proc(1,SIGINT,1)) {
+ if ((machine_state & MACHINE_SHUTTING_DOWN) ||
+ kill_cad_pid(SIGINT, 1)) {
/* No init process or button pressed twice. */
sgi_machine_power_off();
}
diff --git a/arch/mips/sgi-ip32/ip32-reset.c b/arch/mips/sgi-ip32/ip32-reset.c
index 79ddb46..fd0932b 100644
--- a/arch/mips/sgi-ip32/ip32-reset.c
+++ b/arch/mips/sgi-ip32/ip32-reset.c
@@ -120,7 +120,7 @@
if (has_panicked)
return;
- if (shuting_down || kill_proc(1, SIGINT, 1)) {
+ if (shuting_down || kill_cad_pid(SIGINT, 1)) {
/* No init process or button pressed twice. */
ip32_machine_power_off();
}
diff --git a/arch/powerpc/platforms/iseries/mf.c b/arch/powerpc/platforms/iseries/mf.c
index 1a2c2a5..1983b64 100644
--- a/arch/powerpc/platforms/iseries/mf.c
+++ b/arch/powerpc/platforms/iseries/mf.c
@@ -357,7 +357,7 @@
*/
static int shutdown(void)
{
- int rc = kill_proc(1, SIGINT, 1);
+ int rc = kill_cad_pid(SIGINT, 1);
if (rc) {
printk(KERN_ALERT "mf.c: SIGINT to init failed (%d), "
diff --git a/drivers/char/nwbutton.c b/drivers/char/nwbutton.c
index 7c57ebf..ea1aa77 100644
--- a/drivers/char/nwbutton.c
+++ b/drivers/char/nwbutton.c
@@ -127,9 +127,8 @@
static void button_sequence_finished (unsigned long parameters)
{
#ifdef CONFIG_NWBUTTON_REBOOT /* Reboot using button is enabled */
- if (button_press_count == reboot_count) {
- kill_proc (1, SIGINT, 1); /* Ask init to reboot us */
- }
+ if (button_press_count == reboot_count)
+ kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */
#endif /* CONFIG_NWBUTTON_REBOOT */
button_consume_callbacks (button_press_count);
bcount = sprintf (button_output_buffer, "%d\n", button_press_count);
diff --git a/drivers/char/snsc_event.c b/drivers/char/snsc_event.c
index d12d4f6..864854c 100644
--- a/drivers/char/snsc_event.c
+++ b/drivers/char/snsc_event.c
@@ -220,7 +220,7 @@
" Sending SIGPWR to init...\n");
/* give a SIGPWR signal to init proc */
- kill_proc(1, SIGPWR, 0);
+ kill_cad_pid(SIGPWR, 0);
} else {
/* print to system log */
printk("%s|$(0x%x)%s\n", severity, esp_code, desc);
diff --git a/drivers/parisc/power.c b/drivers/parisc/power.c
index fad5a33..4a9f025 100644
--- a/drivers/parisc/power.c
+++ b/drivers/parisc/power.c
@@ -84,8 +84,7 @@
static void deferred_poweroff(void *dummy)
{
- extern int cad_pid; /* from kernel/sys.c */
- if (kill_proc(cad_pid, SIGINT, 1)) {
+ if (kill_cad_pid(SIGINT, 1)) {
/* just in case killing init process failed */
machine_power_off();
}
diff --git a/drivers/s390/s390mach.c b/drivers/s390/s390mach.c
index 479364d..e088b5e 100644
--- a/drivers/s390/s390mach.c
+++ b/drivers/s390/s390mach.c
@@ -208,7 +208,7 @@
*/
__ctl_clear_bit(14, 24); /* Disable WARNING MCH */
if (xchg(&mchchk_wng_posted, 1) == 0)
- kill_proc(1, SIGPWR, 1);
+ kill_cad_pid(SIGPWR, 1);
}
#endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 9ba959e..3853023 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1065,6 +1065,8 @@
return tsk->pid == 1;
}
+extern struct pid *cad_pid;
+
extern void free_task(struct task_struct *tsk);
#define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0)
@@ -1292,6 +1294,11 @@
extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
extern int do_sigaltstack(const stack_t __user *, stack_t __user *, unsigned long);
+static inline int kill_cad_pid(int sig, int priv)
+{
+ return kill_pid(cad_pid, sig, priv);
+}
+
/* These can be the second arg to send_sig_info/send_group_sig_info. */
#define SEND_SIG_NOINFO ((struct siginfo *) 0)
#define SEND_SIG_PRIV ((struct siginfo *) 1)
diff --git a/init/main.c b/init/main.c
index a49b002..ee12324 100644
--- a/init/main.c
+++ b/init/main.c
@@ -721,6 +721,8 @@
*/
child_reaper = current;
+ cad_pid = task_pid(current);
+
smp_prepare_cpus(max_cpus);
do_pre_smp_initcalls();
diff --git a/kernel/sys.c b/kernel/sys.c
index 3a4776e..2314867 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -92,7 +92,8 @@
*/
int C_A_D = 1;
-int cad_pid = 1;
+struct pid *cad_pid;
+EXPORT_SYMBOL(cad_pid);
/*
* Notifier list for kernel code which wants to be called
@@ -773,10 +774,9 @@
if (C_A_D)
schedule_work(&cad_work);
else
- kill_proc(cad_pid, SIGINT, 1);
+ kill_cad_pid(SIGINT, 1);
}
-
/*
* Unprivileged users may change the real gid to the effective gid
* or vice versa. (BSD-style)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index a79ccf9..8020fb2 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -68,7 +68,6 @@
extern int core_uses_pid;
extern int suid_dumpable;
extern char core_pattern[];
-extern int cad_pid;
extern int pid_max;
extern int min_free_kbytes;
extern int printk_ratelimit_jiffies;
@@ -137,6 +136,9 @@
static int proc_do_uts_string(ctl_table *table, int write, struct file *filp,
void __user *buffer, size_t *lenp, loff_t *ppos);
+static int proc_do_cad_pid(ctl_table *table, int write, struct file *filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+
static ctl_table root_table[];
static struct ctl_table_header root_table_header =
{ root_table, LIST_HEAD_INIT(root_table_header.ctl_entry) };
@@ -543,10 +545,10 @@
{
.ctl_name = KERN_CADPID,
.procname = "cad_pid",
- .data = &cad_pid,
+ .data = NULL,
.maxlen = sizeof (int),
.mode = 0600,
- .proc_handler = &proc_dointvec,
+ .proc_handler = &proc_do_cad_pid,
},
{
.ctl_name = KERN_MAX_THREADS,
@@ -2427,6 +2429,28 @@
}
#endif
+static int proc_do_cad_pid(ctl_table *table, int write, struct file *filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct pid *new_pid;
+ pid_t tmp;
+ int r;
+
+ tmp = pid_nr(cad_pid);
+
+ r = __do_proc_dointvec(&tmp, table, write, filp, buffer,
+ lenp, ppos, NULL, NULL);
+ if (r || !write)
+ return r;
+
+ new_pid = find_get_pid(tmp);
+ if (!new_pid)
+ return -ESRCH;
+
+ put_pid(xchg(&cad_pid, new_pid));
+ return 0;
+}
+
#else /* CONFIG_PROC_FS */
int proc_dostring(ctl_table *table, int write, struct file *filp,
