[PATCH] pidspace: is_init()

This is an updated version of Eric Biederman's is_init() patch.
(http://lkml.org/lkml/2006/2/6/280).  It applies cleanly to 2.6.18-rc3 and
replaces a few more instances of ->pid == 1 with is_init().

Further, is_init() checks pid and thus removes dependency on Eric's other
patches for now.

Eric's original description:

	There are a lot of places in the kernel where we test for init
	because we give it special properties.  Most  significantly init
	must not die.  This results in code all over the kernel test
	->pid == 1.

	Introduce is_init to capture this case.

	With multiple pid spaces for all of the cases affected we are
	looking for only the first process on the system, not some other
	process that has pid == 1.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: <lxc-devel@lists.sourceforge.net>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

29 files changed, 41 insertions, 30 deletions

diff --git a/arch/alpha/mm/fault.c b/arch/alpha/mm/fault.c
index 622dabd84680..8871529a34e2 100644
--- a/arch/alpha/mm/fault.c
+++ b/arch/alpha/mm/fault.c
@@ -193,7 +193,7 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
 	/* We ran out of memory, or some other thing happened to us that
 	   made us unable to handle the page fault gracefully.  */
  out_of_memory:
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index a5b33ff3924e..5e658a874498 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -198,7 +198,7 @@ survive:
 		return fault;
 	}
 
-	if (tsk->pid != 1)
+	if (!is_init(tsk))
 		goto out;
 
 	/*
diff --git a/arch/arm26/mm/fault.c b/arch/arm26/mm/fault.c
index a7c4cc922095..a1f6d8a9cc32 100644
--- a/arch/arm26/mm/fault.c
+++ b/arch/arm26/mm/fault.c
@@ -185,7 +185,7 @@ survive:
 	}
 
 	fault = -3; /* out of memory */
-	if (tsk->pid != 1)
+	if (!is_init(tsk))
 		goto out;
 
 	/*
diff --git a/arch/i386/lib/usercopy.c b/arch/i386/lib/usercopy.c
index efc7e7d5f4d0..08502fc6d0cb 100644
--- a/arch/i386/lib/usercopy.c
+++ b/arch/i386/lib/usercopy.c
@@ -739,7 +739,7 @@ survive:
 			retval = get_user_pages(current, current->mm,
 					(unsigned long )to, 1, 1, 0, &pg, NULL);
 
-			if (retval == -ENOMEM && current->pid == 1) {
+			if (retval == -ENOMEM && is_init(current)) {
 				up_read(&current->mm->mmap_sem);
 				blk_congestion_wait(WRITE, HZ/50);
 				goto survive;
diff --git a/arch/i386/mm/fault.c b/arch/i386/mm/fault.c
index 50d8617391dd..2581575786c1 100644
--- a/arch/i386/mm/fault.c
+++ b/arch/i386/mm/fault.c
@@ -589,7 +589,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (tsk->pid == 1) {
+	if (is_init(tsk)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index d8b1b4ac7f26..59f3ab937615 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -280,7 +280,7 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 
   out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/m32r/mm/fault.c b/arch/m32r/mm/fault.c
index dc18a33eefef..8d5f551b5754 100644
--- a/arch/m32r/mm/fault.c
+++ b/arch/m32r/mm/fault.c
@@ -299,7 +299,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (tsk->pid == 1) {
+	if (is_init(tsk)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index 5e2d87c10c87..911f2ce3f53e 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -181,7 +181,7 @@ good_area:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
index a4f8c45c4e8e..8423d8590779 100644
--- a/arch/mips/mm/fault.c
+++ b/arch/mips/mm/fault.c
@@ -171,7 +171,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (tsk->pid == 1) {
+	if (is_init(tsk)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 77953f41d754..e8fa50624b70 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -386,7 +386,7 @@ bad_area_nosemaphore:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index 903115d67fdc..311ed1993fc0 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -337,7 +337,7 @@ static int recover_mce(struct pt_regs *regs, struct rtas_error_log * err)
 		   err->disposition == RTAS_DISP_NOT_RECOVERED &&
 		   err->target == RTAS_TARGET_MEMORY &&
 		   err->type == RTAS_TYPE_ECC_UNCORR &&
-		   !(current->pid == 0 || current->pid == 1)) {
+		   !(current->pid == 0 || is_init(current))) {
 		/* Kill off a user process with an ECC error */
 		printk(KERN_ERR "MCE: uncorrectable ecc error for pid %d\n",
 		       current->pid);
diff --git a/arch/ppc/kernel/traps.c b/arch/ppc/kernel/traps.c
index d7a433049b48..aafc8e8893d1 100644
--- a/arch/ppc/kernel/traps.c
+++ b/arch/ppc/kernel/traps.c
@@ -119,7 +119,7 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr)
 	 * generate the same exception over and over again and we get
 	 * nowhere.  Better to kill it and let the kernel panic.
 	 */
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		__sighandler_t handler;
 
 		spin_lock_irq(&current->sighand->siglock);
diff --git a/arch/ppc/mm/fault.c b/arch/ppc/mm/fault.c
index bc776beb3136..465f451f3bc3 100644
--- a/arch/ppc/mm/fault.c
+++ b/arch/ppc/mm/fault.c
@@ -291,7 +291,7 @@ bad_area:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index f2b9a84dc2bf..9c3c19fe62fc 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -353,7 +353,7 @@ no_context:
 */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (tsk->pid == 1) {
+	if (is_init(tsk)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/sh/mm/fault.c b/arch/sh/mm/fault.c
index 507f28914706..68663b8f99ae 100644
--- a/arch/sh/mm/fault.c
+++ b/arch/sh/mm/fault.c
@@ -149,7 +149,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/sh64/mm/fault.c b/arch/sh64/mm/fault.c
index f08d0eaf6497..8e2f6c28b739 100644
--- a/arch/sh64/mm/fault.c
+++ b/arch/sh64/mm/fault.c
@@ -277,7 +277,7 @@ bad_area:
 			show_regs(regs);
 #endif
 		}
-		if (tsk->pid == 1) {
+		if (is_init(tsk)) {
 			panic("INIT had user mode bad_area\n");
 		}
 		tsk->thread.address = address;
@@ -319,14 +319,14 @@ no_context:
  * us unable to handle the page fault gracefully.
  */
 out_of_memory:
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		panic("INIT out of memory\n");
 		yield();
 		goto survive;
 	}
 	printk("fault:Out of memory\n");
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index 61a23fff4395..c7b195c7e51f 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -120,7 +120,7 @@ out_nosemaphore:
  * us unable to handle the page fault gracefully.
  */
 out_of_memory:
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		up_read(&mm->mmap_sem);
 		yield();
 		down_read(&mm->mmap_sem);
diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index 9ba54cc2b5f6..3751b4788e28 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -244,7 +244,7 @@ static int is_errata93(struct pt_regs *regs, unsigned long address)
 
 int unhandled_signal(struct task_struct *tsk, int sig)
 {
-	if (tsk->pid == 1)
+	if (is_init(tsk))
 		return 1;
 	if (tsk->ptrace & PT_PTRACED)
 		return 0;
@@ -580,7 +580,7 @@ no_context:
  */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) { 
+	if (is_init(current)) {
 		yield();
 		goto again;
 	}
diff --git a/arch/xtensa/mm/fault.c b/arch/xtensa/mm/fault.c
index a945a33e85a1..dd0dbec2e57e 100644
--- a/arch/xtensa/mm/fault.c
+++ b/arch/xtensa/mm/fault.c
@@ -144,7 +144,7 @@ bad_area:
 	 */
 out_of_memory:
 	up_read(&mm->mmap_sem);
-	if (current->pid == 1) {
+	if (is_init(current)) {
 		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index ee3ca8f1768e..0ad6cb081db4 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -208,7 +208,7 @@ static void send_sig_all(int sig)
 	struct task_struct *p;
 
 	for_each_process(p) {
-		if (p->mm && p->pid != 1)
+		if (p->mm && !is_init(p))
 			/* Not swapper, init nor kernel thread */
 			force_sig(sig, p);
 	}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3696f2f7126d..ed2af8671589 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1033,6 +1033,16 @@ static inline int pid_alive(struct task_struct *p)
 	return p->pids[PIDTYPE_PID].pid != NULL;
 }
 
+/**
+ * is_init - check if a task structure is the first user space
+ *	     task the kernel created.
+ * @p: Task structure to be checked.
+ */
+static inline int is_init(struct task_struct *tsk)
+{
+	return tsk->pid == 1;
+}
+
 extern void free_task(struct task_struct *tsk);
 #define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0)
 
diff --git a/kernel/capability.c b/kernel/capability.c
index c7685ad00a97..edb845a6e84a 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -133,7 +133,7 @@ static inline int cap_set_all(kernel_cap_t *effective,
      int found = 0;
 
      do_each_thread(g, target) {
-             if (target == current || target->pid == 1)
+             if (target == current || is_init(target))
                      continue;
              found = 1;
 	     if (security_capset_check(target, effective, inheritable,
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 1b32c2c04c15..584bb4e6c042 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -240,7 +240,7 @@ static struct super_block *cpuset_sb;
  * A cpuset can only be deleted if both its 'count' of using tasks
  * is zero, and its list of 'children' cpusets is empty.  Since all
  * tasks in the system use _some_ cpuset, and since there is always at
- * least one task in the system (init, pid == 1), therefore, top_cpuset
+ * least one task in the system (init), therefore, top_cpuset
  * always has either children cpusets and/or using tasks.  So we don't
  * need a special hack to ensure that top_cpuset cannot be deleted.
  *
diff --git a/kernel/exit.c b/kernel/exit.c
index 4b6fb054b25d..9961192d6055 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -219,7 +219,7 @@ static int will_become_orphaned_pgrp(int pgrp, struct task_struct *ignored_task)
 	do_each_task_pid(pgrp, PIDTYPE_PGID, p) {
 		if (p == ignored_task
 				|| p->exit_state
-				|| p->real_parent->pid == 1)
+				|| is_init(p->real_parent))
 			continue;
 		if (process_group(p->real_parent) != pgrp
 			    && p->real_parent->signal->session == p->signal->session) {
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 50087ecf337e..37cad75cf494 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -40,7 +40,7 @@ struct resource crashk_res = {
 
 int kexec_should_crash(struct task_struct *p)
 {
-	if (in_interrupt() || !p->pid || p->pid == 1 || panic_on_oops)
+	if (in_interrupt() || !p->pid || is_init(p) || panic_on_oops)
 		return 1;
 	return 0;
 }
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 8aad0331d82e..4d50e06fd745 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -440,6 +440,7 @@ struct task_struct *ptrace_get_task_struct(pid_t pid)
 	child = find_task_by_pid(pid);
 	if (child)
 		get_task_struct(child);
+
 	read_unlock(&tasklist_lock);
 	if (!child)
 		return ERR_PTR(-ESRCH);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8bfa7d117c54..9535a3839930 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1915,7 +1915,7 @@ int proc_dointvec_bset(ctl_table *table, int write, struct file *filp,
 		return -EPERM;
 	}
 
-	op = (current->pid == 1) ? OP_SET : OP_AND;
+	op = is_init(current) ? OP_SET : OP_AND;
 	return do_proc_dointvec(table,write,filp,buffer,lenp,ppos,
 				do_proc_dointvec_bset_conv,&op);
 }
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index bada3d03119f..f3dd79c1c367 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -255,7 +255,7 @@ static struct task_struct *select_bad_process(unsigned long *ppoints)
  */
 static void __oom_kill_task(struct task_struct *p, const char *message)
 {
-	if (p->pid == 1) {
+	if (is_init(p)) {
 		WARN_ON(1);
 		printk(KERN_WARNING "tried to kill init!\n");
 		return;
diff --git a/security/commoncap.c b/security/commoncap.c
index f50fc298cf80..5a5ef5ca7ea9 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -169,7 +169,7 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 	/* For init, we want to retain the capabilities set
 	 * in the init_task struct. Thus we skip the usual
 	 * capability rules */
-	if (current->pid != 1) {
+	if (!is_init(current)) {
 		current->cap_permitted = new_permitted;
 		current->cap_effective =
 		    cap_intersect (new_permitted, bprm->cap_effective);