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authorSteven Rostedt <srostedt@redhat.com>2012-11-29 22:27:22 -0500
committerSteven Rostedt <rostedt@goodmis.org>2012-11-30 11:09:28 -0500
commit54f7be5b831254199522523ccab4c3d954bbf576 (patch)
tree7a65782f3bb7f67438db53444b59e8206916d478 /kernel/trace/ring_buffer.c
parent70f77b3f7ec010ff9624c1f2e39a81babc9e2429 (diff)
downloadop-kernel-dev-54f7be5b831254199522523ccab4c3d954bbf576.zip
op-kernel-dev-54f7be5b831254199522523ccab4c3d954bbf576.tar.gz
ring-buffer: Fix NULL pointer if rb_set_head_page() fails
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>
Diffstat (limited to 'kernel/trace/ring_buffer.c')
-rw-r--r--kernel/trace/ring_buffer.c9
1 files 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;
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