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UPSTREAM: kfence, x86: fix preemptible warning on KPTI-enabled systems

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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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

(cherry picked from commit 6a77d38efc)

Bug: 229863099
Signed-off-by: Colin Downs-Razouk <colindr@google.com>
Change-Id: Ia917b052ffbb267254f281f55141c34ad193c78e
This commit is contained in:
Marco Elver
2021-04-09 13:27:44 -07:00
committed by Colin Downs-Razouk
parent e0513ed978
commit aed2e27d51
1 changed files with 6 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
arch/x86/include/asm/kfence.h
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@@ -56,8 +56,13 @@ static inline bool kfence_protect_page(unsigned long addr, bool protect)
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;
}