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

[Fernando Luis Vázquez Cao <fernando@oss.ntt.co.jp>]

This version of the patch does not compile. I will fix this problem and
resend it.
Sorry for the noise.

On Thu, 2006-08-10 at 19:36 +0900, Fernando Luis Vázquez Cao wrote:
> 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@intellilink.co.jp>
> ---
> 
> 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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