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Message-Id: <b3c439c8187f843a03a514f7d8005dc15fcc909e.1550088114.git.khalid.aziz@oracle.com>
Date: Wed, 13 Feb 2019 17:01:25 -0700
From: Khalid Aziz <khalid.aziz@...cle.com>
To: juergh@...il.com, tycho@...ho.ws, jsteckli@...zon.de, ak@...ux.intel.com,
torvalds@...ux-foundation.org, liran.alon@...cle.com,
keescook@...gle.com, akpm@...ux-foundation.org, mhocko@...e.com,
catalin.marinas@....com, will.deacon@....com, jmorris@...ei.org,
konrad.wilk@...cle.com
Cc: Tycho Andersen <tycho@...ker.com>, deepa.srinivasan@...cle.com,
chris.hyser@...cle.com, tyhicks@...onical.com, dwmw@...zon.co.uk,
andrew.cooper3@...rix.com, jcm@...hat.com, boris.ostrovsky@...cle.com,
kanth.ghatraju@...cle.com, oao.m.martins@...cle.com,
jmattson@...gle.com, pradeep.vincent@...cle.com, john.haxby@...cle.com,
tglx@...utronix.de, kirill.shutemov@...ux.intel.com, hch@....de,
steven.sistare@...cle.com, labbott@...hat.com, luto@...nel.org,
dave.hansen@...el.com, peterz@...radead.org,
kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH v8 02/14] x86: always set IF before oopsing from page fault
From: Tycho Andersen <tycho@...ker.com>
Oopsing might kill the task, via rewind_stack_do_exit() at the bottom, and
that might sleep:
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
To be safe, let's just always enable irqs.
The particular case I'm hitting is:
Aug 23 19:30:27 xpfo kernel: [ 38.278615] __bad_area_nosemaphore+0x1a9/0x1d0
Aug 23 19:30:27 xpfo kernel: [ 38.278617] bad_area_nosemaphore+0xf/0x20
Aug 23 19:30:27 xpfo kernel: [ 38.278618] __do_page_fault+0xd1/0x540
Aug 23 19:30:27 xpfo kernel: [ 38.278620] ? irq_work_queue+0x9b/0xb0
Aug 23 19:30:27 xpfo kernel: [ 38.278623] ? wake_up_klogd+0x36/0x40
Aug 23 19:30:27 xpfo kernel: [ 38.278624] trace_do_page_fault+0x3c/0xf0
Aug 23 19:30:27 xpfo kernel: [ 38.278625] do_async_page_fault+0x14/0x60
Aug 23 19:30:27 xpfo kernel: [ 38.278627] async_page_fault+0x28/0x30
When a fault is in kernel space which has been triggered by XPFO.
Signed-off-by: Tycho Andersen <tycho@...ker.com>
CC: x86@...nel.org
Tested-by: Khalid Aziz <khalid.aziz@...cle.com>
---
arch/x86/mm/fault.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 71d4b9d4d43f..ba51652fbd33 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -748,6 +748,12 @@ 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);
}
--
2.17.1
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