From: Alexander Potapenko <glider@google.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Andrey Konovalov <andreyknvl@google.com>,
Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Borislav Petkov <bp@alien8.de>, Christoph Hellwig <hch@lst.de>,
Christoph Lameter <cl@linux.com>,
David Rientjes <rientjes@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Eric Dumazet <edumazet@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
Ilya Leoshkevich <iii@linux.ibm.com>,
Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Kees Cook <keescook@chromium.org>,
Marco Elver <elver@google.com>,
Mark Rutland <mark.rutland@arm.com>,
Matthew Wilcox <willy@infradead.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Pekka Enberg <penberg@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Vasily Gorbik <gor@linux.ibm.com>,
Vegard Nossum <vegard.nossum@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux Memory Management List <linux-mm@kvack.org>,
Linux-Arch <linux-arch@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 28/46] kmsan: entry: handle register passing from uninstrumented code
Date: Mon, 9 May 2022 18:51:59 +0200 [thread overview]
Message-ID: <CAG_fn=X8mc9-_-S-+b9HuF4_-PhN3=1umu5twY8oYn1OgRhuLg@mail.gmail.com> (raw)
In-Reply-To: <CAG_fn=UroTgp0jt77X_E-b1DPJ+32Cye6dRL4DOZ8MRf+XSokg@mail.gmail.com>
On Mon, May 9, 2022 at 6:50 PM Alexander Potapenko <glider@google.com> wrote:
>
> > The callchain is:
> >
> > asm_sysvec_apic_timer_interrupt <- ASM entry in gate
> > sysvec_apic_timer_interrupt(regs) <- noinstr C entry point
> > irqentry_enter(regs) <- unpoisons @reg
> > __sysvec_apic_timer_interrupt(regs) <- the actual handler
> > set_irq_regs(regs) <- stores regs
> > local_apic_timer_interrupt()
> > ...
> > tick_handler() <- One of the 4 variants
> > regs = get_irq_regs(); <- retrieves regs
> > update_process_times(user_tick = user_mode(regs))
> > account_process_tick(user_tick)
> > irqtime_account_process_tick(user_tick)
> > line 382: } else if { user_tick } <- KMSAN complains
> >
> > I'm even more confused now.
>
> Ok, I think I know what's going on.
>
> Indeed, calling kmsan_unpoison_memory() in irqentry_enter() was
> supposed to be enough, but we have code in kmsan_unpoison_memory() (as
> well as other runtime functions) that checks for kmsan_in_runtime()
> and bails out to prevent potential recursion if KMSAN code starts
> calling itself.
>
> kmsan_in_runtime() is implemented as follows:
>
> ==============================================
> static __always_inline bool kmsan_in_runtime(void)
> {
> if ((hardirq_count() >> HARDIRQ_SHIFT) > 1)
> return true;
> return kmsan_get_context()->kmsan_in_runtime;
> }
> ==============================================
> (see the code here:
> https://lore.kernel.org/lkml/20220426164315.625149-13-glider@google.com/#Z31mm:kmsan:kmsan.h)
>
> If we are running in the task context (in_task()==true),
> kmsan_get_context() returns a per-task `struct *kmsan_ctx`.
> If `in_task()==false` and `hardirq_count()>>HARDIRQ_SHIFT==1`, it
> returns a per-CPU one.
> Otherwise kmsan_in_runtime() is considered true to avoid dealing with
> nested interrupts.
>
> So in the case when `hardirq_count()>>HARDIRQ_SHIFT` is greater than
> 1, kmsan_in_runtime() becomes a no-op, which leads to false positives.
Should be "kmsan_unpoison_memory() becomes a no-op..."
next prev parent reply other threads:[~2022-05-09 16:52 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-26 16:42 [PATCH v3 00/46] Add KernelMemorySanitizer infrastructure Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 01/46] x86: add missing include to sparsemem.h Alexander Potapenko
2022-04-27 13:22 ` Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 02/46] stackdepot: reserve 5 extra bits in depot_stack_handle_t Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 03/46] kasan: common: adapt to the new prototype of __stack_depot_save() Alexander Potapenko
2022-04-27 12:47 ` Marco Elver
2022-04-26 16:42 ` [PATCH v3 04/46] instrumented.h: allow instrumenting both sides of copy_from_user() Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 05/46] x86: asm: instrument usercopy in get_user() and __put_user_size() Alexander Potapenko
2022-04-27 3:45 ` kernel test robot
2022-04-27 6:58 ` kernel test robot
2022-04-27 7:14 ` Arnd Bergmann
2022-06-02 11:20 ` Alexander Potapenko
2022-04-27 14:24 ` kernel test robot
2022-04-28 1:59 ` kernel test robot
2022-04-30 10:16 ` [x86] d216de19c8: kernel-selftests.x86.ioperm_32.fail kernel test robot
2022-04-26 16:42 ` [PATCH v3 06/46] asm-generic: instrument usercopy in cacheflush.h Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 07/46] kmsan: add ReST documentation Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 08/46] kmsan: introduce __no_sanitize_memory and __no_kmsan_checks Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 09/46] kmsan: mark noinstr as __no_sanitize_memory Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 10/46] x86: kmsan: pgtable: reduce vmalloc space Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 11/46] libnvdimm/pfn_dev: increase MAX_STRUCT_PAGE_SIZE Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 12/46] kmsan: add KMSAN runtime core Alexander Potapenko
2022-04-27 14:09 ` Marco Elver
2022-05-31 11:08 ` Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 13/46] kmsan: implement kmsan_init(), initialize READ_ONCE_NOCHECK() Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 14/46] kmsan: disable instrumentation of unsupported common kernel code Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 15/46] MAINTAINERS: add entry for KMSAN Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 16/46] kmsan: mm: maintain KMSAN metadata for page operations Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 17/46] kmsan: mm: call KMSAN hooks from SLUB code Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 18/46] kmsan: handle task creation and exiting Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 19/46] kmsan: init: call KMSAN initialization routines Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 20/46] instrumented.h: add KMSAN support Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 21/46] kmsan: unpoison @tlb in arch_tlb_gather_mmu() Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 22/46] kmsan: add iomap support Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 23/46] Input: libps2: mark data received in __ps2_command() as initialized Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 24/46] kmsan: dma: unpoison DMA mappings Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 25/46] kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg() Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 26/46] kmsan: handle memory sent to/from USB Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 27/46] kmsan: instrumentation.h: add instrumentation_begin_with_regs() Alexander Potapenko
2022-04-27 13:28 ` Thomas Gleixner
2022-05-16 11:49 ` Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 28/46] kmsan: entry: handle register passing from uninstrumented code Alexander Potapenko
2022-04-27 13:32 ` Thomas Gleixner
2022-05-02 17:00 ` Alexander Potapenko
2022-05-02 22:00 ` Thomas Gleixner
2022-05-05 18:04 ` Alexander Potapenko
2022-05-05 21:56 ` Thomas Gleixner
2022-05-06 14:52 ` Alexander Potapenko
2022-05-06 16:14 ` Thomas Gleixner
2022-05-06 17:41 ` Alexander Potapenko
2022-05-06 18:41 ` Thomas Gleixner
2022-05-09 16:50 ` Alexander Potapenko
2022-05-09 16:51 ` Alexander Potapenko [this message]
2022-05-09 19:09 ` Thomas Gleixner
2022-05-12 12:24 ` Alexander Potapenko
2022-05-12 16:17 ` Thomas Gleixner
2022-05-12 16:48 ` Thomas Gleixner
2022-06-01 11:27 ` Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 29/46] kmsan: add tests for KMSAN Alexander Potapenko
2022-04-26 16:42 ` [PATCH v3 30/46] kmsan: disable strscpy() optimization under KMSAN Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 31/46] crypto: kmsan: disable accelerated configs " Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 32/46] kmsan: disable physical page merging in biovec Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 33/46] kmsan: block: skip bio block merging logic for KMSAN Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 34/46] kmsan: kcov: unpoison area->list in kcov_remote_area_put() Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 35/46] security: kmsan: fix interoperability with auto-initialization Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 36/46] objtool: kmsan: list KMSAN API functions as uaccess-safe Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 37/46] x86: kmsan: make READ_ONCE_TASK_STACK() return initialized values Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 38/46] x86: kmsan: disable instrumentation of unsupported code Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 39/46] x86: kmsan: skip shadow checks in __switch_to() Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 40/46] x86: kmsan: handle open-coded assembly in lib/iomem.c Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 41/46] x86: kmsan: use __msan_ string functions where possible Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 42/46] x86: kmsan: sync metadata pages on page fault Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 43/46] x86: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 44/46] x86: fs: kmsan: disable CONFIG_DCACHE_WORD_ACCESS Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 45/46] x86: kmsan: handle register passing from uninstrumented code Alexander Potapenko
2022-04-26 16:43 ` [PATCH v3 46/46] x86: kmsan: enable KMSAN builds for x86 Alexander Potapenko
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