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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, andreyknvl@google.com,
	dvyukov@google.com, elver@google.com, glider@google.com,
	jannh@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org,
	tomi.p.sarvela@intel.com, torvalds@linux-foundation.org
Subject: [patch 15/16] kfence, x86: fix preemptible warning on KPTI-enabled systems
Date: Fri, 09 Apr 2021 13:27:44 -0700	[thread overview]
Message-ID: <20210409202744.raBMoNOTx%akpm@linux-foundation.org> (raw)
In-Reply-To: <20210409132633.6855fc8fea1b3905ea1bb4be@linux-foundation.org>

From: Marco Elver <elver@google.com>
Subject: kfence, x86: fix preemptible warning on KPTI-enabled systems

On systems with KPTI enabled, we can currently observe the following
warning:

  BUG: using smp_processor_id() in preemptible
  caller is invalidate_user_asid+0x13/0x50
  CPU: 6 PID: 1075 Comm: dmesg Not tainted 5.12.0-rc4-gda4a2b1a5479-kfence_1+ #1
  Hardware name: Hewlett-Packard HP Pro 3500 Series/2ABF, BIOS 8.11 10/24/2012
  Call Trace:
   dump_stack+0x7f/0xad
   check_preemption_disabled+0xc8/0xd0
   invalidate_user_asid+0x13/0x50
   flush_tlb_one_kernel+0x5/0x20
   kfence_protect+0x56/0x80
   ...

While it normally makes sense to require preemption to be off, so that the
expected CPU's TLB is flushed and not another, in our case it really is
best-effort (see comments in kfence_protect_page()).

Avoid the warning by disabling preemption around flush_tlb_one_kernel().

Link: https://lore.kernel.org/lkml/YGIDBAboELGgMgXy@elver.google.com/
Link: https://lkml.kernel.org/r/20210330065737.652669-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reported-by: Tomi Sarvela <tomi.p.sarvela@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/include/asm/kfence.h |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/kfence.h~kfence-x86-fix-preemptible-warning-on-kpti-enabled-systems
+++ a/arch/x86/include/asm/kfence.h
@@ -56,8 +56,13 @@ static inline bool kfence_protect_page(u
 	else
 		set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT));
 
-	/* Flush this CPU's TLB. */
+	/*
+	 * Flush this CPU's TLB, assuming whoever did the allocation/free is
+	 * likely to continue running on this CPU.
+	 */
+	preempt_disable();
 	flush_tlb_one_kernel(addr);
+	preempt_enable();
 	return true;
 }
 
_

  parent reply	other threads:[~2021-04-09 20:27 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-09 20:26 incoming Andrew Morton
2021-04-09 20:27 ` [patch 01/16] MAINTAINERS: update CZ.NIC's Turris information Andrew Morton
2021-04-09 20:27 ` [patch 02/16] treewide: change my e-mail address, fix my name Andrew Morton
2021-04-09 20:27 ` [patch 03/16] mailmap: update email address for Jordan Crouse Andrew Morton
2021-04-09 20:27 ` [patch 04/16] .mailmap: fix old email addresses Andrew Morton
2021-04-09 20:27 ` [patch 05/16] kasan: fix hwasan build for gcc Andrew Morton
2021-04-09 20:39   ` Andrey Konovalov
2021-04-09 20:58     ` Andrew Morton
2021-04-12  9:56       ` Marco Elver
2021-04-12 12:54         ` Andrey Konovalov
2021-04-09 21:55     ` Linus Torvalds
2021-04-09 20:27 ` [patch 06/16] kasan: remove redundant config option Andrew Morton
2021-04-09 20:27 ` [patch 07/16] mm/gup: check page posion status for coredump Andrew Morton
2021-04-09 20:27 ` [patch 08/16] nds32: flush_dcache_page: use page_mapping_file to avoid races with swapoff Andrew Morton
2021-04-09 20:27 ` [patch 09/16] gcov: re-fix clang-11+ support Andrew Morton
2021-04-09 20:27 ` [patch 10/16] ocfs2: fix deadlock between setattr and dio_end_io_write Andrew Morton
2021-04-09 20:27 ` [patch 11/16] ia64: fix user_stack_pointer() for ptrace() Andrew Morton
2021-04-09 20:27 ` [patch 12/16] fs: direct-io: fix missing sdio->boundary Andrew Morton
2021-04-09 20:27 ` [patch 13/16] kasan: fix conflict with page poisoning Andrew Morton
2021-04-09 20:27 ` [patch 14/16] lib/test_kasan_module.c: suppress unused var warning Andrew Morton
2021-04-09 20:27 ` Andrew Morton [this message]
2021-04-09 20:27 ` [patch 16/16] lib: fix kconfig dependency on ARCH_WANT_FRAME_POINTERS Andrew Morton

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