From patchwork Mon Jan 7 20:36:09 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [3.5.y.z, extended, stable] Patch "ring-buffer: Fix NULL pointer if rb_set_head_page() fails" has been added to staging queue Date: Mon, 07 Jan 2013 10:36:09 -0000 From: Herton Ronaldo Krzesinski X-Patchwork-Id: 210181 Message-Id: <1357590969-20169-1-git-send-email-herton.krzesinski@canonical.com> To: Steven Rostedt Cc: kernel-team@lists.ubuntu.com, Steven Rostedt This is a note to let you know that I have just added a patch titled ring-buffer: Fix NULL pointer if rb_set_head_page() fails to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Herton ------ >From acec2b351ba58a30c7592bb91e937b7ae709b5ca Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 29 Nov 2012 22:27:22 -0500 Subject: [PATCH] ring-buffer: Fix NULL pointer if rb_set_head_page() fails 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 Signed-off-by: Herton Ronaldo Krzesinski --- kernel/trace/ring_buffer.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) -- 1.7.9.5 diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index db6dff1..35bf8f7 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; @@ -3256,6 +3259,8 @@ 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;