[PATCH 4.14 04/16] exit: Add and use make_task_dead.

From: Eric Biggers
Date: Thu Feb 02 2023 - 00:45:58 EST

From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

commit 0e25498f8cd43c1b5aa327f373dd094e9a006da7 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@xxxxxxxxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
arch/alpha/kernel/traps.c | 6 +++---
arch/alpha/mm/fault.c | 2 +-
arch/arm/kernel/traps.c | 2 +-
arch/arm/mm/fault.c | 2 +-
arch/arm64/kernel/traps.c | 2 +-
arch/arm64/mm/fault.c | 2 +-
arch/h8300/kernel/traps.c | 2 +-
arch/h8300/mm/fault.c | 2 +-
arch/hexagon/kernel/traps.c | 2 +-
arch/ia64/kernel/mca_drv.c | 2 +-
arch/ia64/kernel/traps.c | 2 +-
arch/ia64/mm/fault.c | 2 +-
arch/m68k/kernel/traps.c | 2 +-
arch/m68k/mm/fault.c | 2 +-
arch/microblaze/kernel/exceptions.c | 4 ++--
arch/mips/kernel/traps.c | 2 +-
arch/nios2/kernel/traps.c | 4 ++--
arch/openrisc/kernel/traps.c | 2 +-
arch/parisc/kernel/traps.c | 2 +-
arch/powerpc/kernel/traps.c | 2 +-
arch/s390/kernel/dumpstack.c | 2 +-
arch/s390/kernel/nmi.c | 2 +-
arch/sh/kernel/traps.c | 2 +-
arch/sparc/kernel/traps_32.c | 4 +---
arch/sparc/kernel/traps_64.c | 4 +---
arch/x86/entry/entry_32.S | 6 +++---
arch/x86/entry/entry_64.S | 6 +++---
arch/x86/kernel/dumpstack.c | 4 ++--
arch/xtensa/kernel/traps.c | 2 +-
include/linux/sched/task.h | 1 +
kernel/exit.c | 9 +++++++++
tools/objtool/check.c | 3 ++-
32 files changed, 50 insertions(+), 43 deletions(-)

diff --git a/arch/alpha/kernel/traps.c b/arch/alpha/kernel/traps.c
index f43bd05dede26..6a45f392c6728 100644
--- a/arch/alpha/kernel/traps.c
+++ b/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
@@ -609,7 +609,7 @@ 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
@@ -664,7 +664,7 @@ do_entUna(void * va, unsigned long opcode, unsigned long reg,
local_irq_enable();
while (1);
}
- do_exit(SIGSEGV);
+ make_task_dead(SIGSEGV);
}

/*
diff --git a/arch/alpha/mm/fault.c b/arch/alpha/mm/fault.c
index e9392302c5dab..a85c1b18d0bc9 100644
--- a/arch/alpha/mm/fault.c
+++ b/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. */
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 7d81d4a1f5a9c..df7a92c5df6c5 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -342,7 +342,7 @@ 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);
}

/*
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 9bb446cc135d1..45e73596b524c 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -150,7 +150,7 @@ __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);
}

/*
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index b30d23431fe11..ee19e6463e5a4 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -223,7 +223,7 @@ 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);
}

void arm64_notify_die(const char *str, struct pt_regs *regs,
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 617787e4081f1..d191b046d4c18 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -288,7 +288,7 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr,
show_pte(addr);
die("Oops", regs, esr);
bust_spinlocks(0);
- do_exit(SIGKILL);
+ make_task_dead(SIGKILL);
}

/*
diff --git a/arch/h8300/kernel/traps.c b/arch/h8300/kernel/traps.c
index e47a9e0dc278f..a284c126f07a6 100644
--- a/arch/h8300/kernel/traps.c
+++ b/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;
diff --git a/arch/h8300/mm/fault.c b/arch/h8300/mm/fault.c
index fabffb83930af..a8d8fc63780e4 100644
--- a/arch/h8300/mm/fault.c
+++ b/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;
}
diff --git a/arch/hexagon/kernel/traps.c b/arch/hexagon/kernel/traps.c
index 2942a9204a9aa..797608772f8a4 100644
--- a/arch/hexagon/kernel/traps.c
+++ b/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;
}

diff --git a/arch/ia64/kernel/mca_drv.c b/arch/ia64/kernel/mca_drv.c
index 3503d488e9b3f..7c9d63ef1cb28 100644
--- a/arch/ia64/kernel/mca_drv.c
+++ b/arch/ia64/kernel/mca_drv.c
@@ -176,7 +176,7 @@ 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);
}

/**
diff --git a/arch/ia64/kernel/traps.c b/arch/ia64/kernel/traps.c
index 6d4e76a4267f1..2bab65c10d236 100644
--- a/arch/ia64/kernel/traps.c
+++ b/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;
}

diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index dfdc152d6737b..23f23e051ee24 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -300,7 +300,7 @@ 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:
diff --git a/arch/m68k/kernel/traps.c b/arch/m68k/kernel/traps.c
index c1cc4e99aa945..5c72deb117a8e 100644
--- a/arch/m68k/kernel/traps.c
+++ b/arch/m68k/kernel/traps.c
@@ -1141,7 +1141,7 @@ 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)
diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index 127d7c1f2090c..4ef6057592f12 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -50,7 +50,7 @@ int send_fault_sig(struct pt_regs *regs)
pr_alert("Unable to handle kernel access");
pr_cont(" at virtual address %p\n", siginfo.si_addr);
die_if_kernel("Oops", regs, 0 /*error_code*/);
- do_exit(SIGKILL);
+ make_task_dead(SIGKILL);
}

return 1;
diff --git a/arch/microblaze/kernel/exceptions.c b/arch/microblaze/kernel/exceptions.c
index e6f338d0496bb..3066d7fe484bd 100644
--- a/arch/microblaze/kernel/exceptions.c
+++ b/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 */
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index abbc64788008a..a8f166ff2762b 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -414,7 +414,7 @@ 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[];
diff --git a/arch/nios2/kernel/traps.c b/arch/nios2/kernel/traps.c
index 8184e7d6b3857..5dadd36d13ce3 100644
--- a/arch/nios2/kernel/traps.c
+++ b/arch/nios2/kernel/traps.c
@@ -43,10 +43,10 @@ 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)
diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c
index 0d44e8007ad6e..a8fb061f1c888 100644
--- a/arch/openrisc/kernel/traps.c
+++ b/arch/openrisc/kernel/traps.c
@@ -265,7 +265,7 @@ 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 */
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 346456c43aa0b..36582e23f9b9d 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -290,7 +290,7 @@ 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 */
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 05c1aabad01c6..a507a6874d420 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -211,7 +211,7 @@ 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);

diff --git a/arch/s390/kernel/dumpstack.c b/arch/s390/kernel/dumpstack.c
index 2aa545dca4d53..d9513a9f0db12 100644
--- a/arch/s390/kernel/dumpstack.c
+++ b/arch/s390/kernel/dumpstack.c
@@ -186,5 +186,5 @@ 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);
}
diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index 31d03a84126c5..5dca748d3815c 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -94,7 +94,7 @@ 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);
diff --git a/arch/sh/kernel/traps.c b/arch/sh/kernel/traps.c
index 8b49cced663dc..5fafbef7849b1 100644
--- a/arch/sh/kernel/traps.c
+++ b/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)
diff --git a/arch/sparc/kernel/traps_32.c b/arch/sparc/kernel/traps_32.c
index b1ed763e47877..fb0576f3b1de0 100644
--- a/arch/sparc/kernel/traps_32.c
+++ b/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)
- do_exit(SIGKILL);
- do_exit(SIGSEGV);
+ make_task_dead((regs->psr & PSR_PS) ? SIGKILL : SIGSEGV);
}

void do_hw_interrupt(struct pt_regs *regs, unsigned long type)
diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
index 6ab9b87dbca8c..cfc06eeeb4f35 100644
--- a/arch/sparc/kernel/traps_64.c
+++ b/arch/sparc/kernel/traps_64.c
@@ -2547,9 +2547,7 @@ void __noreturn die_if_kernel(char *str, struct pt_regs *regs)
}
if (panic_on_oops)
panic("Fatal exception");
- if (regs->tstate & TSTATE_PRIV)
- do_exit(SIGKILL);
- do_exit(SIGSEGV);
+ make_task_dead((regs->tstate & TSTATE_PRIV)? SIGKILL : SIGSEGV);
}
EXPORT_SYMBOL(die_if_kernel);

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index dbcea4281c309..1fdedb2eaef35 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1068,13 +1068,13 @@ 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)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 637a23d404e95..b57f15b51ed52 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1672,7 +1672,7 @@ ENTRY(ignore_sysret)
sysret
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
@@ -1681,5 +1681,5 @@ ENTRY(rewind_stack_do_exit)
leaq -PTREGS_SIZE(%rax), %rsp
UNWIND_HINT_REGS

- call do_exit
-END(rewind_stack_do_exit)
+ call make_task_dead
+END(rewind_stack_and_make_dead)
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 224de37821e4e..92585a755410b 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -271,7 +271,7 @@ unsigned long oops_begin(void)
EXPORT_SYMBOL_GPL(oops_begin);
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)
{
@@ -303,7 +303,7 @@ 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);

diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 2986bc88a18e7..09ba7436d1bd0 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -547,5 +547,5 @@ 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);
}
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index c3d157a370734..3ef0986cf0ea3 100644
--- a/include/linux/sched/task.h
+++ b/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);

diff --git a/kernel/exit.c b/kernel/exit.c
index 9e70577b818ab..1e778b88fa3fe 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -920,6 +920,15 @@ 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)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 2c8e2dae17016..9048b02b54474 100644
--- a/tools/objtool/check.c
+++ b/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",
@@ -166,7 +167,7 @@ static int __dead_end_function(struct objtool_file *file, struct symbol *func,
"lbug_with_loc",
"fortify_panic",
"machine_real_restart",
- "rewind_stack_do_exit",
+ "rewind_stack_and_make_dead"
};

if (func->bind == STB_WEAK)
--
2.39.1