From: Tycho Andersen <tycho@tycho.ws>
To: Andy Lutomirski <luto@kernel.org>
Cc: Khalid Aziz <khalid.aziz@oracle.com>,
Juerg Haefliger <juergh@gmail.com>,
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Khalid Aziz <khalid@gonehiking.org>
Subject: Re: [RFC PATCH v9 02/13] x86: always set IF before oopsing from page fault
Date: Thu, 4 Apr 2019 09:47:27 -0600 [thread overview]
Message-ID: <20190404154727.GA14030@cisco> (raw)
In-Reply-To: <CALCETrVp37Xo3EMHkeedP1zxUMf9og=mceBa8c55e1F4G1DRSQ@mail.gmail.com>
On Wed, Apr 03, 2019 at 09:12:16PM -0700, Andy Lutomirski wrote:
> On Wed, Apr 3, 2019 at 6:42 PM Tycho Andersen <tycho@tycho.ws> wrote:
> >
> > On Wed, Apr 03, 2019 at 05:12:56PM -0700, Andy Lutomirski wrote:
> > > On Wed, Apr 3, 2019 at 10:36 AM Khalid Aziz <khalid.aziz@oracle.com> wrote:
> > > >
> > > > From: Tycho Andersen <tycho@tycho.ws>
> > > >
> > > > Oopsing might kill the task, via rewind_stack_do_exit() at the bottom, and
> > > > that might sleep:
> > > >
> > >
> > >
> > > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> > > > index 9d5c75f02295..7891add0913f 100644
> > > > --- a/arch/x86/mm/fault.c
> > > > +++ b/arch/x86/mm/fault.c
> > > > @@ -858,6 +858,12 @@ no_context(struct pt_regs *regs, unsigned long error_code,
> > > > /* Executive summary in case the body of the oops scrolled away */
> > > > printk(KERN_DEFAULT "CR2: %016lx\n", address);
> > > >
> > > > + /*
> > > > + * We're about to oops, which might kill the task. Make sure we're
> > > > + * allowed to sleep.
> > > > + */
> > > > + flags |= X86_EFLAGS_IF;
> > > > +
> > > > oops_end(flags, regs, sig);
> > > > }
> > > >
> > >
> > >
> > > NAK. If there's a bug in rewind_stack_do_exit(), please fix it in
> > > rewind_stack_do_exit().
> >
> > [I trimmed the CC list since google rejected it with E2BIG :)]
> >
> > I guess the problem is really that do_exit() (or really
> > exit_signals()) might sleep. Maybe we should put an irq_enable() at
> > the beginning of do_exit() instead and fix this problem for all
> > arches?
> >
>
> Hmm. do_exit() isn't really meant to be "try your best to leave the
> system somewhat usable without returning" -- it's a function that,
> other than in OOPSes, is called from a well-defined state. So I think
> rewind_stack_do_exit() is probably a better spot. But we need to
> rewind the stack and *then* turn on IRQs, since we otherwise risk
> exploding quite badly.
Ok, sounds good. I guess we can include something like this patch in
the next series.
Thanks,
Tycho
From 34dce229a4f43f90db823671eb0b8da7c4906045 Mon Sep 17 00:00:00 2001
From: Tycho Andersen <tycho@tycho.ws>
Date: Thu, 4 Apr 2019 09:41:32 -0600
Subject: [PATCH] x86/entry: re-enable interrupts before exiting
If the kernel oopses in an interrupt, nothing re-enables interrupts:
Aug 23 19:30:27 xpfo kernel: [ 38.302714] BUG: sleeping function called from invalid context at
./include/linux/percpu-rwsem.h:33
Aug 23 19:30:27 xpfo kernel: [ 38.303837] in_atomic(): 0, irqs_disabled(): 1, pid: 1970, name:
lkdtm_xpfo_test
Aug 23 19:30:27 xpfo kernel: [ 38.304758] CPU: 3 PID: 1970 Comm: lkdtm_xpfo_test Tainted: G D
4.13.0-rc5+ #228
Aug 23 19:30:27 xpfo kernel: [ 38.305813] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.10.1-1ubuntu1 04/01/2014
Aug 23 19:30:27 xpfo kernel: [ 38.306926] Call Trace:
Aug 23 19:30:27 xpfo kernel: [ 38.307243] dump_stack+0x63/0x8b
Aug 23 19:30:27 xpfo kernel: [ 38.307665] ___might_sleep+0xec/0x110
Aug 23 19:30:27 xpfo kernel: [ 38.308139] __might_sleep+0x45/0x80
Aug 23 19:30:27 xpfo kernel: [ 38.308593] exit_signals+0x21/0x1c0
Aug 23 19:30:27 xpfo kernel: [ 38.309046] ? blocking_notifier_call_chain+0x11/0x20
Aug 23 19:30:27 xpfo kernel: [ 38.309677] do_exit+0x98/0xbf0
Aug 23 19:30:27 xpfo kernel: [ 38.310078] ? smp_reader+0x27/0x40 [lkdtm]
Aug 23 19:30:27 xpfo kernel: [ 38.310604] ? kthread+0x10f/0x150
Aug 23 19:30:27 xpfo kernel: [ 38.311045] ? read_user_with_flags+0x60/0x60 [lkdtm]
Aug 23 19:30:27 xpfo kernel: [ 38.311680] rewind_stack_do_exit+0x17/0x20
do_exit() expects to be called in a well-defined environment, so let's
re-enable interrupts after unwinding the stack, in case they were disabled.
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
---
arch/x86/entry/entry_32.S | 6 ++++++
arch/x86/entry/entry_64.S | 6 ++++++
2 files changed, 12 insertions(+)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index d309f30cf7af..8ddb7b41669d 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1507,6 +1507,12 @@ ENTRY(rewind_stack_do_exit)
movl PER_CPU_VAR(cpu_current_top_of_stack), %esi
leal -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp
+ /*
+ * If we oopsed in an interrupt handler, interrupts may be off. Let's turn
+ * them back on before going back to "normal" code.
+ */
+ sti
+
call do_exit
1: jmp 1b
END(rewind_stack_do_exit)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 1f0efdb7b629..c0759f3e3ad2 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1672,5 +1672,11 @@ ENTRY(rewind_stack_do_exit)
leaq -PTREGS_SIZE(%rax), %rsp
UNWIND_HINT_FUNC sp_offset=PTREGS_SIZE
+ /*
+ * If we oopsed in an interrupt handler, interrupts may be off. Let's turn
+ * them back on before going back to "normal" code.
+ */
+ sti
+
call do_exit
END(rewind_stack_do_exit)
--
2.19.1
next prev parent reply other threads:[~2019-04-04 15:47 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-03 17:34 [RFC PATCH v9 00/13] Add support for eXclusive Page Frame Ownership Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 01/13] mm: add MAP_HUGETLB support to vm_mmap Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 02/13] x86: always set IF before oopsing from page fault Khalid Aziz
2019-04-04 0:12 ` Andy Lutomirski
2019-04-04 1:42 ` Tycho Andersen
2019-04-04 4:12 ` Andy Lutomirski
2019-04-04 15:47 ` Tycho Andersen [this message]
2019-04-04 16:23 ` Sebastian Andrzej Siewior
2019-04-04 16:28 ` Thomas Gleixner
2019-04-04 17:11 ` Andy Lutomirski
2019-04-03 17:34 ` [RFC PATCH v9 03/13] mm: Add support for eXclusive Page Frame Ownership (XPFO) Khalid Aziz
2019-04-04 7:21 ` Peter Zijlstra
2019-04-04 9:25 ` Peter Zijlstra
2019-04-04 14:48 ` Tycho Andersen
2019-04-04 7:43 ` Peter Zijlstra
2019-04-04 15:15 ` Khalid Aziz
2019-04-04 17:01 ` Peter Zijlstra
2019-04-17 16:15 ` Ingo Molnar
2019-04-17 16:49 ` Khalid Aziz
2019-04-17 17:09 ` Ingo Molnar
2019-04-17 17:19 ` Nadav Amit
2019-04-17 17:26 ` Ingo Molnar
2019-04-17 17:44 ` Nadav Amit
2019-04-17 21:19 ` Thomas Gleixner
2019-04-17 23:18 ` Linus Torvalds
2019-04-17 23:42 ` Thomas Gleixner
2019-04-17 23:52 ` Linus Torvalds
2019-04-18 4:41 ` Andy Lutomirski
2019-04-18 5:41 ` Kees Cook
2019-04-18 14:34 ` Khalid Aziz
2019-04-22 19:30 ` Khalid Aziz
2019-04-22 22:23 ` Kees Cook
2019-04-18 6:14 ` Thomas Gleixner
2019-04-17 17:33 ` Khalid Aziz
2019-04-17 19:49 ` Andy Lutomirski
2019-04-17 19:52 ` Tycho Andersen
2019-04-17 20:12 ` Khalid Aziz
2019-05-01 14:49 ` Waiman Long
2019-05-01 15:18 ` Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 04/13] xpfo, x86: Add support for XPFO for x86-64 Khalid Aziz
2019-04-04 7:52 ` Peter Zijlstra
2019-04-04 15:40 ` Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 05/13] mm: add a user_virt_to_phys symbol Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 06/13] lkdtm: Add test for XPFO Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 07/13] arm64/mm: Add support " Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 08/13] swiotlb: Map the buffer if it was unmapped by XPFO Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 09/13] xpfo: add primitives for mapping underlying memory Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 10/13] arm64/mm, xpfo: temporarily map dcache regions Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 11/13] xpfo, mm: optimize spinlock usage in xpfo_kunmap Khalid Aziz
2019-04-04 7:56 ` Peter Zijlstra
2019-04-04 16:06 ` Khalid Aziz
2019-04-03 17:34 ` [RFC PATCH v9 12/13] xpfo, mm: Defer TLB flushes for non-current CPUs (x86 only) Khalid Aziz
2019-04-04 4:10 ` Andy Lutomirski
[not found] ` <91f1dbce-332e-25d1-15f6-0e9cfc8b797b@oracle.com>
2019-04-05 7:17 ` Thomas Gleixner
2019-04-05 14:44 ` Dave Hansen
2019-04-05 15:24 ` Andy Lutomirski
2019-04-05 15:56 ` Tycho Andersen
2019-04-05 16:32 ` Andy Lutomirski
2019-04-05 15:56 ` Khalid Aziz
2019-04-05 16:01 ` Dave Hansen
2019-04-05 16:27 ` Andy Lutomirski
2019-04-05 16:41 ` Peter Zijlstra
2019-04-05 17:35 ` Khalid Aziz
2019-04-05 15:44 ` Khalid Aziz
2019-04-05 15:24 ` Andy Lutomirski
2019-04-04 8:18 ` Peter Zijlstra
2019-04-03 17:34 ` [RFC PATCH v9 13/13] xpfo, mm: Optimize XPFO TLB flushes by batching them together Khalid Aziz
2019-04-04 16:44 ` [RFC PATCH v9 00/13] Add support for eXclusive Page Frame Ownership Nadav Amit
2019-04-04 17:18 ` Khalid Aziz
2019-04-06 6:40 ` Jon Masters
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