Messages in this thread Patch in this message | | | Subject | [v3.2-v3.4 stable version][PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails | From | Steven Rostedt <> | Date | Wed, 12 Dec 2012 13:44:31 -0500 |
| |
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;
| |