From mboxrd@z Thu Jan 1 00:00:00 1970 From: Khalid Aziz Subject: [RFC PATCH v8 02/14] x86: always set IF before oopsing from page fault Date: Wed, 13 Feb 2019 17:01:25 -0700 Message-Id: In-Reply-To: References: In-Reply-To: References: To: juergh@gmail.com, tycho@tycho.ws, jsteckli@amazon.de, ak@linux.intel.com, torvalds@linux-foundation.org, liran.alon@oracle.com, keescook@google.com, akpm@linux-foundation.org, mhocko@suse.com, catalin.marinas@arm.com, will.deacon@arm.com, jmorris@namei.org, konrad.wilk@oracle.com Cc: Tycho Andersen , deepa.srinivasan@oracle.com, chris.hyser@oracle.com, tyhicks@canonical.com, dwmw@amazon.co.uk, andrew.cooper3@citrix.com, jcm@redhat.com, boris.ostrovsky@oracle.com, kanth.ghatraju@oracle.com, oao.m.martins@oracle.com, jmattson@google.com, pradeep.vincent@oracle.com, john.haxby@oracle.com, tglx@linutronix.de, kirill.shutemov@linux.intel.com, hch@lst.de, steven.sistare@oracle.com, labbott@redhat.com, luto@kernel.org, dave.hansen@intel.com, peterz@infradead.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org List-ID: From: Tycho Andersen 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 CC: x86@kernel.org Tested-by: Khalid Aziz --- 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