[v3.2-v3.4 stable version][PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails

[v3.2-v3.4 stable version][PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails

[Steven Rostedt]

The function rb_set_head_page() searches the list of ring buffer
pages for a the page that has the HEAD page flag set. If it does
not find it, it will do a WARN_ON(), disable the ring buffer and
return NULL, as this should never happen.

But if this bug happens to happen, not all callers of this function
can handle a NULL pointer being returned from it. That needs to be
fixed.

Cc: stable@vger.kernel.org # 3.0+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

Index: linux-test.git/kernel/trace/ring_buffer.c
===================================================================
--- linux-test.git.orig/kernel/trace/ring_buffer.c
+++ linux-test.git/kernel/trace/ring_buffer.c
@@ -2683,7 +2683,7 @@ unsigned long ring_buffer_oldest_event_t
 	unsigned long flags;
 	struct ring_buffer_per_cpu *cpu_buffer;
 	struct buffer_page *bpage;
-	unsigned long ret;
+	unsigned long ret = 0;
 
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return 0;
@@ -2698,7 +2698,8 @@ unsigned long ring_buffer_oldest_event_t
 		bpage = cpu_buffer->reader_page;
 	else
 		bpage = rb_set_head_page(cpu_buffer);
-	ret = bpage->page->time_stamp;
+	if (bpage)
+		ret = bpage->page->time_stamp;
 	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
 	return ret;
@@ -3005,6 +3006,8 @@ rb_get_reader_page(struct ring_buffer_pe
 	 * Splice the empty reader page into the list around the head.
 	 */
 	reader = rb_set_head_page(cpu_buffer);
+	if (!reader)
+		goto out;
 	cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
 	cpu_buffer->reader_page->list.prev = reader->list.prev;
 

Re: [v3.2-v3.4 stable version][PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails

[Ben Hutchings]

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On Wed, 2012-12-12 at 13:44 -0500, Steven Rostedt wrote:
> The function rb_set_head_page() searches the list of ring buffer
> pages for a the page that has the HEAD page flag set. If it does
> not find it, it will do a WARN_ON(), disable the ring buffer and
> return NULL, as this should never happen.
> 
> But if this bug happens to happen, not all callers of this function
> can handle a NULL pointer being returned from it. That needs to be
> fixed.
> 
> Cc: stable@vger.kernel.org # 3.0+
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[...]

Queued up for 3.2, thanks.

Ben.

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[PATCH 0/2] [GIT PULL][v3.7] ring-buffer: Bug fixes

[Steven Rostedt]

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Ingo,

This is based off of my last urgent pull request.

Please pull the latest tip/perf/urgent-2 tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
tip/perf/urgent-2

Head SHA1: 9366c1ba13fbc41bdb57702e75ca4382f209c82f


Steven Rostedt (2):
      ring-buffer: Fix NULL pointer if rb_set_head_page() fails
      ring-buffer: Fix race between integrity check and readers

----
 kernel/trace/ring_buffer.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

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[PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails

[Steven Rostedt]

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From: Steven Rostedt <srostedt@redhat.com>

The function rb_set_head_page() searches the list of ring buffer
pages for a the page that has the HEAD page flag set. If it does
not find it, it will do a WARN_ON(), disable the ring buffer and
return NULL, as this should never happen.

But if this bug happens to happen, not all callers of this function
can handle a NULL pointer being returned from it. That needs to be
fixed.

Cc: stable@vger.kernel.org # 3.0+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index b979426..ec01803 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1396,6 +1396,8 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
 		struct list_head *head_page_with_bit;
 
 		head_page = &rb_set_head_page(cpu_buffer)->list;
+		if (!head_page)
+			break;
 		prev_page = head_page->prev;
 
 		first_page = pages->next;
@@ -2934,7 +2936,7 @@ unsigned long ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
 	unsigned long flags;
 	struct ring_buffer_per_cpu *cpu_buffer;
 	struct buffer_page *bpage;
-	unsigned long ret;
+	unsigned long ret = 0;
 
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return 0;
@@ -2949,7 +2951,8 @@ unsigned long ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
 		bpage = cpu_buffer->reader_page;
 	else
 		bpage = rb_set_head_page(cpu_buffer);
-	ret = bpage->page->time_stamp;
+	if (bpage)
+		ret = bpage->page->time_stamp;
 	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
 	return ret;
@@ -3260,6 +3263,8 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
 	 * Splice the empty reader page into the list around the head.
 	 */
 	reader = rb_set_head_page(cpu_buffer);
+	if (!reader)
+		goto out;
 	cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
 	cpu_buffer->reader_page->list.prev = reader->list.prev;
 
-- 
1.7.10.4



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[v3.2-v3.4 stable version][PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails

[Steven Rostedt]

The function rb_set_head_page() searches the list of ring buffer
pages for a the page that has the HEAD page flag set. If it does
not find it, it will do a WARN_ON(), disable the ring buffer and
return NULL, as this should never happen.

But if this bug happens to happen, not all callers of this function
can handle a NULL pointer being returned from it. That needs to be
fixed.

Cc: stable@vger.kernel.org # 3.0+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

Index: linux-test.git/kernel/trace/ring_buffer.c
===================================================================
--- linux-test.git.orig/kernel/trace/ring_buffer.c
+++ linux-test.git/kernel/trace/ring_buffer.c
@@ -2683,7 +2683,7 @@ unsigned long ring_buffer_oldest_event_t
 	unsigned long flags;
 	struct ring_buffer_per_cpu *cpu_buffer;
 	struct buffer_page *bpage;
-	unsigned long ret;
+	unsigned long ret = 0;
 
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return 0;
@@ -2698,7 +2698,8 @@ unsigned long ring_buffer_oldest_event_t
 		bpage = cpu_buffer->reader_page;
 	else
 		bpage = rb_set_head_page(cpu_buffer);
-	ret = bpage->page->time_stamp;
+	if (bpage)
+		ret = bpage->page->time_stamp;
 	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
 	return ret;
@@ -3005,6 +3006,8 @@ rb_get_reader_page(struct ring_buffer_pe
 	 * Splice the empty reader page into the list around the head.
 	 */
 	reader = rb_set_head_page(cpu_buffer);
+	if (!reader)
+		goto out;
 	cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
 	cpu_buffer->reader_page->list.prev = reader->list.prev;
 

Re: [v3.2-v3.4 stable version][PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails

[Ben Hutchings]

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On Fri, 2012-11-30 at 11:18 -0500, Steven Rostedt wrote:
> The function rb_set_head_page() searches the list of ring buffer
> pages for a the page that has the HEAD page flag set. If it does
> not find it, it will do a WARN_ON(), disable the ring buffer and
> return NULL, as this should never happen.
> 
> But if this bug happens to happen, not all callers of this function
> can handle a NULL pointer being returned from it. That needs to be
> fixed.
> 
> Cc: stable@vger.kernel.org # 3.0+
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[...]

Added to the queue for 3.2, thanks.

Ben.

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