Commit 06039754 authored by Fernando Luis Vzquez Cao's avatar Fernando Luis Vzquez Cao Committed by Andi Kleen
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[PATCH] i386: Disallow kprobes on NMI handlers 



A kprobe executes IRET early and that could cause NMI recursion and stack
corruption.

Note: This problem was originally spotted and solved by Andi Kleen in the
x86_64 architecture. This patch is an adaption of his patch for i386.

AK: Merged with current code which was a bit different.
AK: Removed printk in nmi handler that shouldn't be there in the first time
AK: Added missing include.
AK: added KPROBES_END

Signed-off-by: default avatarFernando Vazquez <fernando@intellilink.co.jp>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent 6f6b1e04

arch/i386/kernel/entry.S

+2 −1
Original line number Diff line number Diff line
@@ -729,7 +729,7 @@ KPROBE_END(debug) 
 * check whether we got an NMI on the debug path where the debug

 * fault happened on the sysenter path.

 */

ENTRY(nmi)

KPROBE_ENTRY(nmi)

	RING0_INT_FRAME

	pushl %eax

	CFI_ADJUST_CFA_OFFSET 4
@@ -805,6 +805,7 @@ nmi_16bit_stack: 
	.align 4

	.long 1b,iret_exc

.previous

KPROBE_END(nmi)



KPROBE_ENTRY(int3)

	RING0_INT_FRAME

arch/i386/kernel/nmi.c

+3 −3
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/sysctl.h>

#include <linux/percpu.h>

#include <linux/dmi.h>

#include <linux/kprobes.h>



#include <asm/smp.h>

#include <asm/nmi.h>
@@ -882,7 +883,7 @@ EXPORT_SYMBOL(touch_nmi_watchdog); 


extern void die_nmi(struct pt_regs *, const char *msg);



int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason)

__kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason)

{



	/*
@@ -962,8 +963,7 @@ int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason) 
			 * This matches the old behaviour.

			 */

			rc = 1;

		} else

			printk(KERN_WARNING "Unknown enabled NMI hardware?!\n");

		}

	}

done:

	return rc;

arch/i386/kernel/traps.c

+9 −6
Original line number Diff line number Diff line
@@ -689,7 +689,8 @@ gp_in_kernel: 
	}

}



static void mem_parity_error(unsigned char reason, struct pt_regs * regs)

static __kprobes void

mem_parity_error(unsigned char reason, struct pt_regs * regs)

{

	printk(KERN_EMERG "Uhhuh. NMI received for unknown reason %02x on "

		"CPU %d.\n", reason, smp_processor_id());
@@ -704,7 +705,8 @@ static void mem_parity_error(unsigned char reason, struct pt_regs * regs) 
	clear_mem_error(reason);

}



static void io_check_error(unsigned char reason, struct pt_regs * regs)

static __kprobes void

io_check_error(unsigned char reason, struct pt_regs * regs)

{

	unsigned long i;
@@ -720,7 +722,8 @@ static void io_check_error(unsigned char reason, struct pt_regs * regs) 
	outb(reason, 0x61);

}



static void unknown_nmi_error(unsigned char reason, struct pt_regs * regs)

static __kprobes void

unknown_nmi_error(unsigned char reason, struct pt_regs * regs)

{

#ifdef CONFIG_MCA

	/* Might actually be able to figure out what the guilty party
@@ -741,7 +744,7 @@ static void unknown_nmi_error(unsigned char reason, struct pt_regs * regs) 


static DEFINE_SPINLOCK(nmi_print_lock);



void die_nmi (struct pt_regs *regs, const char *msg)

void __kprobes die_nmi(struct pt_regs *regs, const char *msg)

{

	if (notify_die(DIE_NMIWATCHDOG, msg, regs, 0, 2, SIGINT) ==

	    NOTIFY_STOP)
@@ -773,7 +776,7 @@ void die_nmi (struct pt_regs *regs, const char *msg) 
	do_exit(SIGSEGV);

}



static void default_do_nmi(struct pt_regs * regs)

static __kprobes void default_do_nmi(struct pt_regs * regs)

{

	unsigned char reason = 0;
@@ -811,7 +814,7 @@ static void default_do_nmi(struct pt_regs * regs) 
	reassert_nmi();

}



fastcall void do_nmi(struct pt_regs * regs, long error_code)

fastcall __kprobes void do_nmi(struct pt_regs * regs, long error_code)

{

	int cpu;

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