[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/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,
