exit: Add and use make_task_dead.

commit 0e25498f8c upstream.

There are two big uses of do_exit.  The first is it's design use to be
the guts of the exit(2) system call.  The second use is to terminate
a task after something catastrophic has happened like a NULL pointer
in kernel code.

Add a function make_task_dead that is initialy exactly the same as
do_exit to cover the cases where do_exit is called to handle
catastrophic failure.  In time this can probably be reduced to just a
light wrapper around do_task_dead. For now keep it exactly the same so
that there will be no behavioral differences introducing this new
concept.

Replace all of the uses of do_exit that use it for catastraphic
task cleanup with make_task_dead to make it clear what the code
is doing.

As part of this rename rewind_stack_do_exit
rewind_stack_and_make_dead.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/alpha/kernel/traps.c

@@ -192,7 +192,7 @@ die_if_kernel(char * str, struct pt_regs *regs, long err, unsigned long *r9_15)
 		local_irq_enable();
 		while (1);
 	}
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }
 
 #ifndef CONFIG_MATHEMU
@@ -577,7 +577,7 @@ do_entUna(void * va, unsigned long opcode, unsigned long reg,
 
 	printk("Bad unaligned kernel access at %016lx: %p %lx %lu\n",
 		pc, va, opcode, reg);
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 
 got_exception:
 	/* Ok, we caught the exception, but we don't want it.  Is there
@@ -632,7 +632,7 @@ do_entUna(void * va, unsigned long opcode, unsigned long reg,
 		local_irq_enable();
 		while (1);
 	}
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }
 
 /*

arch/alpha/mm/fault.c

@@ -206,7 +206,7 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
 	printk(KERN_ALERT "Unable to handle kernel paging request at "
 	       "virtual address %016lx\n", address);
 	die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
-	do_exit(SIGKILL);
+	make_task_dead(SIGKILL);
 
 	/* We ran out of memory, or some other thing happened to us that
 	   made us unable to handle the page fault gracefully.  */

arch/arm/kernel/traps.c

@@ -344,7 +344,7 @@ static void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 	if (panic_on_oops)
 		panic("Fatal exception");
 	if (signr)
-		do_exit(signr);
+		make_task_dead(signr);
 }
 
 /*

arch/arm/mm/fault.c

@@ -149,7 +149,7 @@ __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 	show_pte(mm, addr);
 	die("Oops", regs, fsr);
 	bust_spinlocks(0);
-	do_exit(SIGKILL);
+	make_task_dead(SIGKILL);
 }
 
 /*

arch/arm64/kernel/traps.c

@@ -224,7 +224,7 @@ void die(const char *str, struct pt_regs *regs, int err)
 	raw_spin_unlock_irqrestore(&die_lock, flags);
 
 	if (ret != NOTIFY_STOP)
-		do_exit(SIGSEGV);
+		make_task_dead(SIGSEGV);
 }
 
 static bool show_unhandled_signals_ratelimited(void)

arch/arm64/mm/fault.c

@@ -268,7 +268,7 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
 	show_pte(addr);
 	die("Oops", regs, esr);
 	bust_spinlocks(0);
-	do_exit(SIGKILL);
+	make_task_dead(SIGKILL);
 }
 
 static void __do_kernel_fault(unsigned long addr, unsigned int esr,

arch/h8300/kernel/traps.c

@@ -110,7 +110,7 @@ void die(const char *str, struct pt_regs *fp, unsigned long err)
 	dump(fp);
 
 	spin_unlock_irq(&die_lock);
-	do_exit(SIGSEGV);
+	make_dead_task(SIGSEGV);
 }
 
 static int kstack_depth_to_print = 24;

arch/h8300/mm/fault.c

@@ -52,7 +52,7 @@ asmlinkage int do_page_fault(struct pt_regs *regs, unsigned long address,
 	printk(" at virtual address %08lx\n", address);
 	if (!user_mode(regs))
 		die("Oops", regs, error_code);
-	do_exit(SIGKILL);
+	make_dead_task(SIGKILL);
 
 	return 1;
 }

arch/hexagon/kernel/traps.c

@@ -234,7 +234,7 @@ int die(const char *str, struct pt_regs *regs, long err)
 		panic("Fatal exception");
 
 	oops_exit();
-	do_exit(err);
+	make_dead_task(err);
 	return 0;
 }
 

arch/ia64/kernel/mca_drv.c

@@ -11,6 +11,7 @@
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/sched.h>
+#include <linux/sched/task.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/kallsyms.h>
@@ -176,7 +177,7 @@ mca_handler_bh(unsigned long paddr, void *iip, unsigned long ipsr)
 	spin_unlock(&mca_bh_lock);
 
 	/* This process is about to be killed itself */
-	do_exit(SIGKILL);
+	make_task_dead(SIGKILL);
 }
 
 /**

arch/ia64/kernel/traps.c

@@ -85,7 +85,7 @@ die (const char *str, struct pt_regs *regs, long err)
 	if (panic_on_oops)
 		panic("Fatal exception");
 
-  	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 	return 0;
 }
 

arch/ia64/mm/fault.c

@@ -302,7 +302,7 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
 		regs = NULL;
 	bust_spinlocks(0);
 	if (regs)
-		do_exit(SIGKILL);
+		make_task_dead(SIGKILL);
 	return;
 
   out_of_memory:

arch/m68k/kernel/traps.c

@@ -1139,7 +1139,7 @@ void die_if_kernel (char *str, struct pt_regs *fp, int nr)
 	pr_crit("%s: %08x\n", str, nr);
 	show_registers(fp);
 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }
 
 asmlinkage void set_esp0(unsigned long ssp)

arch/m68k/mm/fault.c

@@ -48,7 +48,7 @@ int send_fault_sig(struct pt_regs *regs)
 			pr_alert("Unable to handle kernel access");
 		pr_cont(" at virtual address %p\n", addr);
 		die_if_kernel("Oops", regs, 0 /*error_code*/);
-		do_exit(SIGKILL);
+		make_task_dead(SIGKILL);
 	}
 
 	return 1;

arch/microblaze/kernel/exceptions.c

@@ -44,10 +44,10 @@ void die(const char *str, struct pt_regs *fp, long err)
 	pr_warn("Oops: %s, sig: %ld\n", str, err);
 	show_regs(fp);
 	spin_unlock_irq(&die_lock);
-	/* do_exit() should take care of panic'ing from an interrupt
+	/* make_task_dead() should take care of panic'ing from an interrupt
 	 * context so we don't handle it here
 	 */
-	do_exit(err);
+	make_task_dead(err);
 }
 
 /* for user application debugging */

arch/mips/kernel/traps.c

@@ -412,7 +412,7 @@ void __noreturn die(const char *str, struct pt_regs *regs)
 	if (regs && kexec_should_crash(current))
 		crash_kexec(regs);
 
-	do_exit(sig);
+	make_task_dead(sig);
 }
 
 extern struct exception_table_entry __start___dbe_table[];

arch/nds32/kernel/traps.c

@@ -183,7 +183,7 @@ void die(const char *str, struct pt_regs *regs, int err)
 
 	bust_spinlocks(0);
 	spin_unlock_irq(&die_lock);
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }
 
 EXPORT_SYMBOL(die);
@@ -286,7 +286,7 @@ void unhandled_interruption(struct pt_regs *regs)
 	pr_emerg("unhandled_interruption\n");
 	show_regs(regs);
 	if (!user_mode(regs))
-		do_exit(SIGKILL);
+		make_task_dead(SIGKILL);
 	force_sig(SIGKILL, current);
 }
 
@@ -297,7 +297,7 @@ void unhandled_exceptions(unsigned long entry, unsigned long addr,
 		 addr, type);
 	show_regs(regs);
 	if (!user_mode(regs))
-		do_exit(SIGKILL);
+		make_task_dead(SIGKILL);
 	force_sig(SIGKILL, current);
 }
 
@@ -324,7 +324,7 @@ void do_revinsn(struct pt_regs *regs)
 	pr_emerg("Reserved Instruction\n");
 	show_regs(regs);
 	if (!user_mode(regs))
-		do_exit(SIGILL);
+		make_task_dead(SIGILL);
 	force_sig(SIGILL, current);
 }
 

arch/nios2/kernel/traps.c

@@ -37,10 +37,10 @@ void die(const char *str, struct pt_regs *regs, long err)
 	show_regs(regs);
 	spin_unlock_irq(&die_lock);
 	/*
-	 * do_exit() should take care of panic'ing from an interrupt
+	 * make_task_dead() should take care of panic'ing from an interrupt
 	 * context so we don't handle it here
 	 */
-	do_exit(err);
+	make_task_dead(err);
 }
 
 void _exception(int signo, struct pt_regs *regs, int code, unsigned long addr)

arch/openrisc/kernel/traps.c

@@ -224,7 +224,7 @@ void die(const char *str, struct pt_regs *regs, long err)
 	__asm__ __volatile__("l.nop   1");
 	do {} while (1);
 #endif
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }
 
 /* This is normally the 'Oops' routine */

arch/parisc/kernel/traps.c

@@ -265,7 +265,7 @@ void die_if_kernel(char *str, struct pt_regs *regs, long err)
 		panic("Fatal exception");
 
 	oops_exit();
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }
 
 /* gdb uses break 4,8 */

arch/powerpc/kernel/traps.c

@@ -251,7 +251,7 @@ static void oops_end(unsigned long flags, struct pt_regs *regs,
 		panic("Fatal exception in interrupt");
 	if (panic_on_oops)
 		panic("Fatal exception");
-	do_exit(signr);
+	make_task_dead(signr);
 }
 NOKPROBE_SYMBOL(oops_end);
 

arch/riscv/kernel/traps.c

@@ -64,7 +64,7 @@ void die(struct pt_regs *regs, const char *str)
 	if (panic_on_oops)
 		panic("Fatal exception");
 	if (ret != NOTIFY_STOP)
-		do_exit(SIGSEGV);
+		make_task_dead(SIGSEGV);
 }
 
 void do_trap(struct pt_regs *regs, int signo, int code,

arch/riscv/mm/fault.c

@@ -200,7 +200,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 		(addr < PAGE_SIZE) ? "NULL pointer dereference" :
 		"paging request", addr);
 	die(regs, "Oops");
-	do_exit(SIGKILL);
+	make_task_dead(SIGKILL);
 
 	/*
 	 * We ran out of memory, call the OOM killer, and return the userspace

arch/s390/kernel/dumpstack.c

@@ -187,5 +187,5 @@ void die(struct pt_regs *regs, const char *str)
 	if (panic_on_oops)
 		panic("Fatal exception: panic_on_oops");
 	oops_exit();
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }

arch/s390/kernel/nmi.c

@@ -179,7 +179,7 @@ void s390_handle_mcck(void)
 		       "malfunction (code 0x%016lx).\n", mcck.mcck_code);
 		printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
 		       current->comm, current->pid);
-		do_exit(SIGSEGV);
+		make_task_dead(SIGSEGV);
 	}
 }
 EXPORT_SYMBOL_GPL(s390_handle_mcck);

arch/sh/kernel/traps.c

@@ -57,7 +57,7 @@ void die(const char *str, struct pt_regs *regs, long err)
 	if (panic_on_oops)
 		panic("Fatal exception");
 
-	do_exit(SIGSEGV);
+	make_task_dead(SIGSEGV);
 }
 
 void die_if_kernel(const char *str, struct pt_regs *regs, long err)

arch/sparc/kernel/traps_32.c

@@ -86,9 +86,7 @@ void __noreturn die_if_kernel(char *str, struct pt_regs *regs)
 	}
 	printk("Instruction DUMP:");
 	instruction_dump ((unsigned long *) regs->pc);
-	if(regs->psr & PSR_PS)
+	make_task_dead((regs->psr & PSR_PS) ? SIGKILL : SIGSEGV);
-		do_exit(SIGKILL);
-	do_exit(SIGSEGV);
 }
 
 void do_hw_interrupt(struct pt_regs *regs, unsigned long type)

arch/sparc/kernel/traps_64.c

@@ -2565,9 +2565,7 @@ void __noreturn die_if_kernel(char *str, struct pt_regs *regs)
 	}
 	if (panic_on_oops)
 		panic("Fatal exception");
-	if (regs->tstate & TSTATE_PRIV)
+	make_task_dead((regs->tstate & TSTATE_PRIV)? SIGKILL : SIGSEGV);
-		do_exit(SIGKILL);
-	do_exit(SIGSEGV);
 }
 EXPORT_SYMBOL(die_if_kernel);
 

arch/x86/entry/entry_32.S

@@ -1500,13 +1500,13 @@ ENTRY(async_page_fault)
 END(async_page_fault)
 #endif
 
-ENTRY(rewind_stack_do_exit)
+ENTRY(rewind_stack_and_make_dead)
 	/* Prevent any naive code from trying to unwind to our caller. */
 	xorl	%ebp, %ebp
 
 	movl	PER_CPU_VAR(cpu_current_top_of_stack), %esi
 	leal	-TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp
 
-	call	do_exit
+	call	make_task_dead
 1:	jmp 1b
-END(rewind_stack_do_exit)
+END(rewind_stack_and_make_dead)

arch/x86/entry/entry_64.S

@@ -1762,7 +1762,7 @@ ENTRY(ignore_sysret)
 	sysretl
 END(ignore_sysret)
 
-ENTRY(rewind_stack_do_exit)
+ENTRY(rewind_stack_and_make_dead)
 	UNWIND_HINT_FUNC
 	/* Prevent any naive code from trying to unwind to our caller. */
 	xorl	%ebp, %ebp
@@ -1771,5 +1771,5 @@ ENTRY(rewind_stack_do_exit)
 	leaq	-PTREGS_SIZE(%rax), %rsp
 	UNWIND_HINT_REGS
 
-	call	do_exit
+	call	make_task_dead
-END(rewind_stack_do_exit)
+END(rewind_stack_and_make_dead)

arch/x86/kernel/dumpstack.c

@@ -326,7 +326,7 @@ unsigned long oops_begin(void)
 }
 NOKPROBE_SYMBOL(oops_begin);
 
-void __noreturn rewind_stack_do_exit(int signr);
+void __noreturn rewind_stack_and_make_dead(int signr);
 
 void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 {
@@ -361,7 +361,7 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 	 * reuse the task stack and that existing poisons are invalid.
 	 */
 	kasan_unpoison_task_stack(current);
-	rewind_stack_do_exit(signr);
+	rewind_stack_and_make_dead(signr);
 }
 NOKPROBE_SYMBOL(oops_end);
 

arch/xtensa/kernel/traps.c

@@ -542,5 +542,5 @@ void die(const char * str, struct pt_regs * regs, long err)
 	if (panic_on_oops)
 		panic("Fatal exception");
 
-	do_exit(err);
+	make_task_dead(err);
 }

include/linux/sched/task.h

@@ -36,6 +36,7 @@ extern int sched_fork(unsigned long clone_flags, struct task_struct *p);
 extern void sched_dead(struct task_struct *p);
 
 void __noreturn do_task_dead(void);
+void __noreturn make_task_dead(int signr);
 
 extern void proc_caches_init(void);
 

kernel/exit.c

@@ -922,6 +922,15 @@ void __noreturn do_exit(long code)
 }
 EXPORT_SYMBOL_GPL(do_exit);
 
+void __noreturn make_task_dead(int signr)
+{
+	/*
+	 * Take the task off the cpu after something catastrophic has
+	 * happened.
+	 */
+	do_exit(signr);
+}
+
 void complete_and_exit(struct completion *comp, long code)
 {
 	if (comp)

tools/objtool/check.c

@@ -159,6 +159,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"panic",
 		"do_exit",
 		"do_task_dead",
+		"make_task_dead",
 		"__module_put_and_exit",
 		"complete_and_exit",
 		"kvm_spurious_fault",
@@ -167,7 +168,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"fortify_panic",
 		"usercopy_abort",
 		"machine_real_restart",
-		"rewind_stack_do_exit",
+		"rewind_stack_and_make_dead"
 	};
 
 	if (func->bind == STB_WEAK)