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Commit fef47e2a authored by Helge Deller's avatar Helge Deller
Browse files

parisc: ratelimit userspace segfault printing 



Ratelimit printing of userspace segfaults and make it runtime
configurable via the /proc/sys/debug/exception-trace variable. This
should resolve syslog from growing way too fast and thus prevents
possible system service attacks.

Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # 3.13+
parent 455c6fdb

arch/parisc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ config PARISC 
	select GENERIC_SMP_IDLE_THREAD

	select GENERIC_STRNCPY_FROM_USER

	select SYSCTL_ARCH_UNALIGN_ALLOW

	select SYSCTL_EXCEPTION_TRACE

	select HAVE_MOD_ARCH_SPECIFIC

	select VIRT_TO_BUS

	select MODULES_USE_ELF_RELA

arch/parisc/kernel/traps.c

+25 −29
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <linux/interrupt.h>

#include <linux/console.h>

#include <linux/bug.h>

#include <linux/ratelimit.h>



#include <asm/assembly.h>

#include <asm/uaccess.h>
@@ -42,9 +43,6 @@ 


#include "../math-emu/math-emu.h"	/* for handle_fpe() */



#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */

			  /*  dumped to the console via printk)          */



#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)

DEFINE_SPINLOCK(pa_dbit_lock);

#endif
@@ -160,6 +158,17 @@ void show_regs(struct pt_regs *regs) 
	}

}



static DEFINE_RATELIMIT_STATE(_hppa_rs,

	DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);



#define parisc_printk_ratelimited(critical, regs, fmt, ...)	{	      \

	if ((critical || show_unhandled_signals) && __ratelimit(&_hppa_rs)) { \

		printk(fmt, ##__VA_ARGS__);				      \

		show_regs(regs);					      \

	}								      \

}





static void do_show_stack(struct unwind_frame_info *info)

{

	int i = 1;
@@ -229,12 +238,10 @@ void die_if_kernel(char *str, struct pt_regs *regs, long err) 
		if (err == 0)

			return; /* STFU */



		printk(KERN_CRIT "%s (pid %d): %s (code %ld) at " RFMT "\n",

		parisc_printk_ratelimited(1, regs,

			KERN_CRIT "%s (pid %d): %s (code %ld) at " RFMT "\n",

			current->comm, task_pid_nr(current), str, err, regs->iaoq[0]);

#ifdef PRINT_USER_FAULTS

		/* XXX for debugging only */

		show_regs(regs);

#endif



		return;

	}
@@ -321,14 +328,11 @@ static void handle_break(struct pt_regs *regs) 
			(tt == BUG_TRAP_TYPE_NONE) ? 9 : 0);

	}



#ifdef PRINT_USER_FAULTS

	if (unlikely(iir != GDB_BREAK_INSN)) {

		printk(KERN_DEBUG "break %d,%d: pid=%d command='%s'\n",

	if (unlikely(iir != GDB_BREAK_INSN))

		parisc_printk_ratelimited(0, regs,

			KERN_DEBUG "break %d,%d: pid=%d command='%s'\n",

			iir & 31, (iir>>13) & ((1<<13)-1),

			task_pid_nr(current), current->comm);

		show_regs(regs);

	}

#endif



	/* send standard GDB signal */

	handle_gdb_break(regs, TRAP_BRKPT);
@@ -758,11 +762,9 @@ void notrace handle_interruption(int code, struct pt_regs *regs) 


	default:

		if (user_mode(regs)) {

#ifdef PRINT_USER_FAULTS

			printk(KERN_DEBUG "\nhandle_interruption() pid=%d command='%s'\n",

			parisc_printk_ratelimited(0, regs, KERN_DEBUG

				"handle_interruption() pid=%d command='%s'\n",

				task_pid_nr(current), current->comm);

			show_regs(regs);

#endif

			/* SIGBUS, for lack of a better one. */

			si.si_signo = SIGBUS;

			si.si_code = BUS_OBJERR;
@@ -779,16 +781,10 @@ void notrace handle_interruption(int code, struct pt_regs *regs) 


	if (user_mode(regs)) {

	    if ((fault_space >> SPACEID_SHIFT) != (regs->sr[7] >> SPACEID_SHIFT)) {

#ifdef PRINT_USER_FAULTS

		if (fault_space == 0)

			printk(KERN_DEBUG "User Fault on Kernel Space ");

		else

			printk(KERN_DEBUG "User Fault (long pointer) (fault %d) ",

			       code);

		printk(KERN_CONT "pid=%d command='%s'\n",

		parisc_printk_ratelimited(0, regs, KERN_DEBUG

				"User fault %d on space 0x%08lx, pid=%d command='%s'\n",

				code, fault_space,

				task_pid_nr(current), current->comm);

		show_regs(regs);

#endif

		si.si_signo = SIGSEGV;

		si.si_errno = 0;

		si.si_code = SEGV_MAPERR;

arch/parisc/mm/fault.c

+30 −14
Original line number Diff line number Diff line
@@ -19,10 +19,6 @@ 
#include <asm/uaccess.h>

#include <asm/traps.h>



#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */

			 /*  dumped to the console via printk)          */





/* Various important other fields */

#define bit22set(x)		(x & 0x00000200)

#define bits23_25set(x)		(x & 0x000001c0)
@@ -34,6 +30,8 @@ 


DEFINE_PER_CPU(struct exception_data, exception_data);



int show_unhandled_signals = 1;



/*

 * parisc_acctyp(unsigned int inst) --

 *    Given a PA-RISC memory access instruction, determine if the
@@ -173,6 +171,32 @@ int fixup_exception(struct pt_regs *regs) 
	return 0;

}



/*

 * Print out info about fatal segfaults, if the show_unhandled_signals

 * sysctl is set:

 */

static inline void

show_signal_msg(struct pt_regs *regs, unsigned long code,

		unsigned long address, struct task_struct *tsk,

		struct vm_area_struct *vma)

{

	if (!unhandled_signal(tsk, SIGSEGV))

		return;



	if (!printk_ratelimit())

		return;



	pr_warn("\n");

	pr_warn("do_page_fault() command='%s' type=%lu address=0x%08lx",

	    tsk->comm, code, address);

	print_vma_addr(KERN_CONT " in ", regs->iaoq[0]);

	if (vma)

		pr_warn(" vm_start = 0x%08lx, vm_end = 0x%08lx\n",

				vma->vm_start, vma->vm_end);



	show_regs(regs);

}



void do_page_fault(struct pt_regs *regs, unsigned long code,

			      unsigned long address)

{
@@ -270,16 +294,8 @@ bad_area: 
	if (user_mode(regs)) {

		struct siginfo si;



#ifdef PRINT_USER_FAULTS

		printk(KERN_DEBUG "\n");

		printk(KERN_DEBUG "do_page_fault() pid=%d command='%s' type=%lu address=0x%08lx\n",

		    task_pid_nr(tsk), tsk->comm, code, address);

		if (vma) {

			printk(KERN_DEBUG "vm_start = 0x%08lx, vm_end = 0x%08lx\n",

					vma->vm_start, vma->vm_end);

		}

		show_regs(regs);

#endif

		show_signal_msg(regs, code, address, tsk, vma);



		switch (code) {

		case 15:	/* Data TLB miss fault/Data page fault */

			/* send SIGSEGV when outside of vma */