[PATCH 1/2] i386: Disallow kprobes on NMI handlers

[Fernando Luis Vázquez Cao]

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 <fernando@xxxxxxxxxxxxxxxxx>
---

diff -urNp linux-2.6.18-rc4-orig/arch/i386/kernel/entry.S linux-2.6.18-rc4/arch/i386/kernel/entry.S
--- linux-2.6.18-rc4-orig/arch/i386/kernel/entry.S	2006-08-10 17:24:14.000000000 +0900
+++ linux-2.6.18-rc4/arch/i386/kernel/entry.S	2006-08-10 17:31:55.000000000 +0900
@@ -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
--- linux-2.6.18-rc4-orig/arch/i386/kernel/nmi.c	2006-08-10 17:24:15.000000000 +0900
+++ linux-2.6.18-rc4/arch/i386/kernel/nmi.c	2006-08-10 17:40:22.000000000 +0900
@@ -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
--- linux-2.6.18-rc4-orig/arch/i386/kernel/traps.c	2006-08-10 17:24:16.000000000 +0900
+++ linux-2.6.18-rc4/arch/i386/kernel/traps.c	2006-08-10 18:16:12.000000000 +0900
@@ -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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