This is a note to let you know that I've just added the patch titled
ring-buffer: Fix NULL pointer if rb_set_head_page() fails
to the 3.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ring-buffer-fix-null-pointer-if-rb_set_head_page-fails.patch
and it can be found in the queue-3.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 54f7be5b831254199522523ccab4c3d954bbf576 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <[email protected]>
Date: Thu, 29 Nov 2012 22:27:22 -0500
Subject: ring-buffer: Fix NULL pointer if rb_set_head_page() fails
From: Steven Rostedt <[email protected]>
commit 54f7be5b831254199522523ccab4c3d954bbf576 upstream.
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.
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/trace/ring_buffer.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1396,6 +1396,8 @@ rb_insert_pages(struct ring_buffer_per_c
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_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;
@@ -2949,7 +2951,8 @@ 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;
@@ -3260,6 +3263,8 @@ 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;
Patches currently in stable-queue which might be from [email protected] are
queue-3.6/ring-buffer-fix-null-pointer-if-rb_set_head_page-fails.patch
queue-3.6/ring-buffer-fix-race-between-integrity-check-and-readers.patch
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