[PATCH] kprobes: fix bug when probed on task and isr functions

This patch fixes a race condition where in system used to hang or sometime
crash within minutes when kprobes are inserted on ISR routine and a task
routine.

The fix has been stress tested on i386, ia64, pp64 and on x86_64.  To
reproduce the problem insert kprobes on schedule() and do_IRQ() functions
and you should see hang or system crash.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 5 deletions

diff --git a/arch/ppc64/kernel/kprobes.c b/arch/ppc64/kernel/kprobes.c
index 591e4b67b5a5..7e80d49c589a 100644
--- a/arch/ppc64/kernel/kprobes.c
+++ b/arch/ppc64/kernel/kprobes.c
@@ -102,7 +102,7 @@ static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
         regs->msr |= MSR_SE;
 
         /* single step inline if it is a trap variant */
-        if (IS_TW(insn) || IS_TD(insn) || IS_TWI(insn) || IS_TDI(insn))
+        if (is_trap(insn))
                 regs->nip = (unsigned long)p->addr;
         else
                 regs->nip = (unsigned long)p->ainsn.insn;
@@ -152,7 +152,9 @@ static inline int kprobe_handler(struct pt_regs *regs)
                    Disarm the probe we just hit, and ignore it. */
                 p = get_kprobe(addr);
                 if (p) {
-                        if (kprobe_status == KPROBE_HIT_SS) {
+                        kprobe_opcode_t insn = *p->ainsn.insn;
+                        if (kprobe_status == KPROBE_HIT_SS &&
+                                        is_trap(insn)) {
                                 regs->msr &= ~MSR_SE;
                                 regs->msr |= kprobe_saved_msr;
                                 unlock_kprobes();
@@ -192,8 +194,7 @@ static inline int kprobe_handler(struct pt_regs *regs)
                          * trap variant, it could belong to someone else
                          */
                         kprobe_opcode_t cur_insn = *addr;
-                        if (IS_TW(cur_insn) || IS_TD(cur_insn) ||
-                                        IS_TWI(cur_insn) || IS_TDI(cur_insn))
+                        if (is_trap(cur_insn))
                                 goto no_kprobe;
                         /*
                          * The breakpoint instruction was removed right
@@ -403,7 +404,7 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
         default:
                 break;
         }
-        preempt_enable();
+        preempt_enable_no_resched();
         return ret;
 }