Messages in this thread | | | From | Kees Cook <> | Date | Thu, 8 Sep 2016 08:52:33 -0700 | Subject | Re: [list] 8052ce2d97: WARNING: CPU: 0 PID: 1 at lib/list_debug.c:60 __list_del_entry+0x4d/0x71 |
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On Thu, Sep 8, 2016 at 2:27 AM, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > On Wed, Sep 07, 2016 at 10:25:58AM -0700, Kees Cook wrote: >> On Wed, Sep 7, 2016 at 12:31 AM, Paul E. McKenney >> <paulmck@linux.vnet.ibm.com> wrote: >> > On Tue, Sep 06, 2016 at 11:49:04AM -0400, Kees Cook wrote: >> >> On Sun, Sep 4, 2016 at 5:48 AM, Paul E. McKenney >> >> <paulmck@linux.vnet.ibm.com> wrote: >> >> > On Sun, Sep 04, 2016 at 08:35:40AM +0800, kernel test robot wrote: >> >> >> >> >> >> FYI, we noticed the following commit: >> >> >> >> >> >> https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2016.08.19a >> >> >> commit 8052ce2d9771ab5a818307f3abbaf33bba82a631 ("list: Split list_add() debug checking into separate function") >> >> >> >> >> >> in testcase: boot >> >> >> >> >> >> on test machine: qemu-system-i386 -enable-kvm -m 360M >> >> >> >> >> >> caused below changes: >> >> > >> >> > Hello, Kees, >> >> > >> >> > Looks like your change might have actually found a bug. ;-) >> >> > >> >> > How would you like to handle this? >> >> >> >> We should fix the bug! :) >> > >> > But of course... >> > >> > The question is whether I am considered to be fully responsible for >> > chasing down any bugs that arise. It is looking like I am, in which >> > case I must defer this patch to the 4.10 merge window. Things are a >> > bit crazy now due to prior overcommitments... >> >> I'm going to double-check the code, but the changes I made shouldn't >> have changed any of the logical checks under CONFIG_DEBUG_LIST... just >> the manifestation of WARN vs BUG. So, since both this and the BPF RCU >> bug have appeared, something has changed... I will go digging... > > So maybe the boot failures are a result of the WARN->BUG transition? > >> >> >> [ 152.698509] ------------[ cut here ]------------ >> >> >> [ 152.709786] WARNING: CPU: 0 PID: 1 at lib/list_debug.c:60 __list_del_entry+0x4d/0x71 >> >> >> [ 152.722785] list_del corruption. next->prev should be cc0230d4, but was 6b6b6b6b >> >> >> >> That's the poison value, so this is a remove-after-remove bug?
Unfortunately, the 0-day backtrace shows WARN :(
-Kees
-- Kees Cook Nexus Security
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