From: Sukadev Bhattiprolu <sukadev@us.ibm.com>

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>
---

 arch/alpha/mm/fault.c                |    2 +-
 arch/arm/mm/fault.c                  |    2 +-
 arch/arm26/mm/fault.c                |    2 +-
 arch/i386/lib/usercopy.c             |    2 +-
 arch/i386/mm/fault.c                 |    2 +-
 arch/ia64/mm/fault.c                 |    2 +-
 arch/m32r/mm/fault.c                 |    2 +-
 arch/m68k/mm/fault.c                 |    2 +-
 arch/mips/mm/fault.c                 |    2 +-
 arch/powerpc/mm/fault.c              |    2 +-
 arch/powerpc/platforms/pseries/ras.c |    2 +-
 arch/ppc/kernel/traps.c              |    2 +-
 arch/ppc/mm/fault.c                  |    2 +-
 arch/s390/mm/fault.c                 |    2 +-
 arch/sh/mm/fault.c                   |    2 +-
 arch/sh64/mm/fault.c                 |    6 +++---
 arch/um/kernel/trap.c                |    2 +-
 arch/x86_64/mm/fault.c               |    4 ++--
 arch/xtensa/mm/fault.c               |    2 +-
 drivers/char/sysrq.c                 |    2 +-
 include/linux/sched.h                |   10 ++++++++++
 kernel/capability.c                  |    2 +-
 kernel/cpuset.c                      |    2 +-
 kernel/exit.c                        |    2 +-
 kernel/kexec.c                       |    2 +-
 kernel/ptrace.c                      |    1 +
 kernel/sysctl.c                      |    2 +-
 mm/oom_kill.c                        |    2 +-
 security/commoncap.c                 |    2 +-
 29 files changed, 41 insertions(+), 30 deletions(-)

diff -puN arch/alpha/mm/fault.c~pidspace-is_init arch/alpha/mm/fault.c
--- a/arch/alpha/mm/fault.c~pidspace-is_init
+++ a/arch/alpha/mm/fault.c
@@ -193,7 +193,7 @@ do_page_fault(unsigned long address, uns
 	/* 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 -puN arch/arm/mm/fault.c~pidspace-is_init arch/arm/mm/fault.c
--- a/arch/arm/mm/fault.c~pidspace-is_init
+++ a/arch/arm/mm/fault.c
@@ -198,7 +198,7 @@ survive:
 		return fault;
 	}
 
-	if (tsk->pid != 1)
+	if (!is_init(tsk))
 		goto out;
 
 	/*
diff -puN arch/arm26/mm/fault.c~pidspace-is_init arch/arm26/mm/fault.c
--- a/arch/arm26/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/i386/lib/usercopy.c~pidspace-is_init arch/i386/lib/usercopy.c
--- a/arch/i386/lib/usercopy.c~pidspace-is_init
+++ a/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 -puN arch/i386/mm/fault.c~pidspace-is_init arch/i386/mm/fault.c
--- a/arch/i386/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/ia64/mm/fault.c~pidspace-is_init arch/ia64/mm/fault.c
--- a/arch/ia64/mm/fault.c~pidspace-is_init
+++ a/arch/ia64/mm/fault.c
@@ -280,7 +280,7 @@ ia64_do_page_fault (unsigned long addres
 
   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 -puN arch/m32r/mm/fault.c~pidspace-is_init arch/m32r/mm/fault.c
--- a/arch/m32r/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/m68k/mm/fault.c~pidspace-is_init arch/m68k/mm/fault.c
--- a/arch/m68k/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/mips/mm/fault.c~pidspace-is_init arch/mips/mm/fault.c
--- a/arch/mips/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/powerpc/mm/fault.c~pidspace-is_init arch/powerpc/mm/fault.c
--- a/arch/powerpc/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/powerpc/platforms/pseries/ras.c~pidspace-is_init arch/powerpc/platforms/pseries/ras.c
--- a/arch/powerpc/platforms/pseries/ras.c~pidspace-is_init
+++ a/arch/powerpc/platforms/pseries/ras.c
@@ -337,7 +337,7 @@ static int recover_mce(struct pt_regs *r
 		   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 -puN arch/ppc/kernel/traps.c~pidspace-is_init arch/ppc/kernel/traps.c
--- a/arch/ppc/kernel/traps.c~pidspace-is_init
+++ a/arch/ppc/kernel/traps.c
@@ -119,7 +119,7 @@ void _exception(int signr, struct pt_reg
 	 * 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 -puN arch/ppc/mm/fault.c~pidspace-is_init arch/ppc/mm/fault.c
--- a/arch/ppc/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/s390/mm/fault.c~pidspace-is_init arch/s390/mm/fault.c
--- a/arch/s390/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/sh/mm/fault.c~pidspace-is_init arch/sh/mm/fault.c
--- a/arch/sh/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/sh64/mm/fault.c~pidspace-is_init arch/sh64/mm/fault.c
--- a/arch/sh64/mm/fault.c~pidspace-is_init
+++ a/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 -puN arch/um/kernel/trap.c~pidspace-is_init arch/um/kernel/trap.c
--- a/arch/um/kernel/trap.c~pidspace-is_init
+++ a/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 -puN arch/x86_64/mm/fault.c~pidspace-is_init arch/x86_64/mm/fault.c
--- a/arch/x86_64/mm/fault.c~pidspace-is_init
+++ a/arch/x86_64/mm/fault.c
@@ -244,7 +244,7 @@ static int is_errata93(struct pt_regs *r
 
 int unhandled_signal(struct task_struct *tsk, int sig)
 {
-	if (tsk->pid == 1)
+	if (is_init(tsk))
 		return 1;
 	if (tsk->p