linux-kernel - [tip:perf/probes] kprobes: Prevent re-registration of the same kprobe

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Date:	Sat, 17 Oct 2009 10:02:09 GMT
From:	tip-bot for Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	mingo@...hat.com, peterz@...radead.org, fweisbec@...il.com,
	rostedt@...dmis.org, ak@...ux.intel.com, jbaron@...hat.com,
	tglx@...utronix.de, laijs@...fujitsu.com, mhiramat@...hat.com,
	linux-kernel@...r.kernel.org, hpa@...or.com, fche@...hat.com,
	jkenisto@...ibm.com, tzanussi@...il.com, lizf@...fujitsu.com,
	hch@...radead.org, ananth@...ibm.com, srikar@...ux.vnet.ibm.com,
	mingo@...e.hu, prasad@...ux.vnet.ibm.com
Subject: [tip:perf/probes] kprobes: Prevent re-registration of the same kprobe

Commit-ID:  1f0ab40976460bc4673fa204ce917a725185d8f2
Gitweb:     http://git.kernel.org/tip/1f0ab40976460bc4673fa204ce917a725185d8f2
Author:     Ananth N Mavinakayanahalli <ananth@...ibm.com>
AuthorDate: Tue, 15 Sep 2009 10:43:07 +0530
Committer:  Frederic Weisbecker <fweisbec@...il.com>
CommitDate: Thu, 17 Sep 2009 04:24:57 +0200

kprobes: Prevent re-registration of the same kprobe

Prevent re-registration of the same kprobe. This situation, though
unlikely, needs to be flagged since it can lead to a system crash if
it's not handled.

The core change itself is small, but the helper routine needed to be
moved around a bit; hence the diffstat.

Signed-off-by: Ananth N Mavinakayanahalli<ananth@...ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Jim Keniston <jkenisto@...ibm.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Frank Ch. Eigler <fche@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Jason Baron <jbaron@...hat.com>
Cc: K.Prasad <prasad@...ux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Li Zefan <lizf@...fujitsu.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Tom Zanussi <tzanussi@...il.com>
LKML-Reference: <20090915051307.GB26458@...ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
---
 kernel/kprobes.c |   58 +++++++++++++++++++++++++++++++++++------------------
 1 files changed, 38 insertions(+), 20 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 00d01b0..b946761 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -676,6 +676,40 @@ static kprobe_opcode_t __kprobes *kprobe_addr(struct kprobe *p)
 	return (kprobe_opcode_t *)(((char *)addr) + p->offset);
 }
 
+/* Check passed kprobe is valid and return kprobe in kprobe_table. */
+static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p)
+{
+	struct kprobe *old_p, *list_p;
+
+	old_p = get_kprobe(p->addr);
+	if (unlikely(!old_p))
+		return NULL;
+
+	if (p != old_p) {
+		list_for_each_entry_rcu(list_p, &old_p->list, list)
+			if (list_p == p)
+			/* kprobe p is a valid probe */
+				goto valid;
+		return NULL;
+	}
+valid:
+	return old_p;
+}
+
+/* Return error if the kprobe is being re-registered */
+static inline int check_kprobe_rereg(struct kprobe *p)
+{
+	int ret = 0;
+	struct kprobe *old_p;
+
+	mutex_lock(&kprobe_mutex);
+	old_p = __get_valid_kprobe(p);
+	if (old_p)
+		ret = -EINVAL;
+	mutex_unlock(&kprobe_mutex);
+	return ret;
+}
+
 int __kprobes register_kprobe(struct kprobe *p)
 {
 	int ret = 0;
@@ -688,6 +722,10 @@ int __kprobes register_kprobe(struct kprobe *p)
 		return -EINVAL;
 	p->addr = addr;
 
+	ret = check_kprobe_rereg(p);
+	if (ret)
+		return ret;
+
 	preempt_disable();
 	if (!kernel_text_address((unsigned long) p->addr) ||
 	    in_kprobes_functions((unsigned long) p->addr)) {
@@ -757,26 +795,6 @@ out:
 }
 EXPORT_SYMBOL_GPL(register_kprobe);
 
-/* Check passed kprobe is valid and return kprobe in kprobe_table. */
-static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p)
-{
-	struct kprobe *old_p, *list_p;
-
-	old_p = get_kprobe(p->addr);
-	if (unlikely(!old_p))
-		return NULL;
-
-	if (p != old_p) {
-		list_for_each_entry_rcu(list_p, &old_p->list, list)
-			if (list_p == p)
-			/* kprobe p is a valid probe */
-				goto valid;
-		return NULL;
-	}
-valid:
-	return old_p;
-}
-
 /*
  * Unregister a kprobe without a scheduler synchronization.
  */
--
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