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| author | Steven Rostedt <srostedt@redhat.com> | 2012-11-29 22:27:22 -0500 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2012-11-30 11:09:28 -0500 |
| commit | 54f7be5b831254199522523ccab4c3d954bbf576 (patch) | |
| tree | 7a65782f3bb7f67438db53444b59e8206916d478 /kernel/trace/ring_buffer.c | |
| parent | 70f77b3f7ec010ff9624c1f2e39a81babc9e2429 (diff) | |
| download | lwn-54f7be5b831254199522523ccab4c3d954bbf576.tar.gz lwn-54f7be5b831254199522523ccab4c3d954bbf576.zip | |
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.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b979426d16c6..ec01803e0a55 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; |