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 identified and solved by Andi Kleen in the x86_64 architecture. This patch is an adaption of his patch for i386.

Signed-off-by Fernando Vazquez <[email protected]>

---

diff -urNp linux-2.6.18-rc4-orig/arch/i386/kernel/entry.S linux-2.6.18-rc4/arch/i386/kernel/entry.S

arch/i386/kernel/entry.S +1 -1

@@ -725,7 +725,7 @@ debug_stack_correct:
  * 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

diff -urNp linux-2.6.18-rc4-orig/arch/i386/kernel/nmi.c linux-2.6.18-rc4/arch/i386/kernel/nmi.c

arch/i386/kernel/nmi.c +1 -1

@@ -579,7 +579,7 @@ EXPORT_SYMBOL(touch_nmi_watchdog);
 
 extern void die_nmi(struct pt_regs *, const char *msg);
 
-void nmi_watchdog_tick (struct pt_regs * regs)
+void __kprobes nmi_watchdog_tick (struct pt_regs * regs)
 {
 
 	/*

diff -urNp linux-2.6.18-rc4-orig/arch/i386/kernel/traps.c linux-2.6.18-rc4/arch/i386/kernel/traps.c

arch/i386/kernel/traps.c +10 -8

@@ -626,7 +626,8 @@ 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. Dazed and confused, but trying "
 			"to continue\n");

@@ -637,7 +638,8 @@ static void mem_parity_error(unsigned ch
 	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;
 

@@ -653,7 +655,8 @@ static void io_check_error(unsigned char
 	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

@@ -671,7 +674,7 @@ static void unknown_nmi_error(unsigned c
 
 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)

@@ -703,7 +706,7 @@ void die_nmi (struct pt_regs *regs, cons
 	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;
 

@@ -741,14 +744,14 @@ static void default_do_nmi(struct pt_reg
 	reassert_nmi();
 }
 
-static int dummy_nmi_callback(struct pt_regs * regs, int cpu)
+static __kprobes int dummy_nmi_callback(struct pt_regs * regs, int cpu)
 {
 	return 0;
 }
 
 static nmi_callback_t nmi_callback = dummy_nmi_callback;
 
-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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