linux-kernel - [PATCH 3.16 244/328] ring-buffer: Allow for rescheduling when removing pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1544392233.938234578@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        "Vaibhav Nagarnaik" <vnagarnaik@...gle.com>,
        "Jason Behmer" <jbehmer@...gle.com>
Subject: [PATCH 3.16 244/328] ring-buffer: Allow for rescheduling when
 removing pages

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vaibhav Nagarnaik <vnagarnaik@...gle.com>

commit 83f365554e47997ec68dc4eca3f5dce525cd15c3 upstream.

When reducing ring buffer size, pages are removed by scheduling a work
item on each CPU for the corresponding CPU ring buffer. After the pages
are removed from ring buffer linked list, the pages are free()d in a
tight loop. The loop does not give up CPU until all pages are removed.
In a worst case behavior, when lot of pages are to be freed, it can
cause system stall.

After the pages are removed from the list, the free() can happen while
the work is rescheduled. Call cond_resched() in the loop to prevent the
system hangup.

Link: http://lkml.kernel.org/r/20180907223129.71994-1-vnagarnaik@google.com

Fixes: 83f40318dab00 ("ring-buffer: Make removal of ring buffer pages atomic")
Reported-by: Jason Behmer <jbehmer@...gle.com>
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@...gle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/trace/ring_buffer.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1541,6 +1541,8 @@ rb_remove_pages(struct ring_buffer_per_c
 	tmp_iter_page = first_page;

 	do {
+		cond_resched();
+
 		to_remove_page = tmp_iter_page;
 		rb_inc_page(cpu_buffer, &tmp_iter_page);