[PATCH 3.13 127/212] parisc: ratelimit userspace segfault printing

Kamal Mostafa
2014-06-17T21:43:41Z

From: Helge Deller <deller@gmx.de>

commit fef47e2a2e1e75fe50a10f634a80f16808348cc6 upstream.

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: Helge Deller <deller@gmx.de>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
arch/parisc/Kconfig | 1 +
arch/parisc/kernel/traps.c | 54 +++++++++++++++++++++-------------------------
arch/parisc/mm/fault.c | 44 +++++++++++++++++++++++++------------
3 files changed, 56 insertions(+), 43 deletions(-)

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index b5f1858..2142ec2 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -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
diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 1cd1d0c..47ee620 100644
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -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",
- task_pid_nr(current), current->comm);
- show_regs(regs);
-#endif
+ parisc_printk_ratelimited(0, regs, KERN_DEBUG
+ "handle_interruption() pid=%d command='%s'\n",
+ task_pid_nr(current), current->comm);
/* 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",
- task_pid_nr(current), current->comm);
- show_regs(regs);
-#endif
+ 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);
si.si_signo = SIGSEGV;
si.si_errno = 0;
si.si_code = SEGV_MAPERR;
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 9d08c71..d72197f 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -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 */
--
1.9.1