[PATCH v5 0/2] kasan: Fix metadata detection for KASAN_HW_TAGS

[Vincenzo Frascino]

With the introduction of KASAN_HW_TAGS, kasan_report() currently assumes
that every location in memory has valid metadata associated. This is due
to the fact that addr_has_metadata() returns always true.

As a consequence of this, an invalid address (e.g. NULL pointer address)
passed to kasan_report() when KASAN_HW_TAGS is enabled, leads to a
kernel panic.

Example below, based on arm64:

 ==================================================================
 BUG: KASAN: invalid-access in 0x0
 Read at addr 0000000000000000 by task swapper/0/1
 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
 Mem abort info:
   ESR = 0x96000004
   EC = 0x25: DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
 Data abort info:
   ISV = 0, ISS = 0x00000004
   CM = 0, WnR = 0

...

 Call trace:
  mte_get_mem_tag+0x24/0x40
  kasan_report+0x1a4/0x410
  alsa_sound_last_init+0x8c/0xa4
  do_one_initcall+0x50/0x1b0
  kernel_init_freeable+0x1d4/0x23c
  kernel_init+0x14/0x118
  ret_from_fork+0x10/0x34
 Code: d65f03c0 9000f021 f9428021 b6cfff61 (d9600000)
 ---[ end trace 377c8bb45bdd3a1a ]---
 hrtimer: interrupt took 48694256 ns
 note: swapper/0[1] exited with preempt_count 1
 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
 SMP: stopping secondary CPUs
 Kernel Offset: 0x35abaf140000 from 0xffff800010000000
 PHYS_OFFSET: 0x40000000
 CPU features: 0x0a7e0152,61c0a030
 Memory Limit: none
 ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---

This series fixes the behavior of addr_has_metadata() that now returns
true only when the address is valid.

Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin at virtuozzo.com>
Cc: Alexander Potapenko <glider at google.com>
Cc: Dmitry Vyukov <dvyukov at google.com>
Cc: Leon Romanovsky <leonro at mellanox.com>
Cc: Andrey Konovalov <andreyknvl at google.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Paul E. McKenney <paulmck at kernel.org>
Cc: Naresh Kamboju <naresh.kamboju at linaro.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>

Vincenzo Frascino (2):
  kasan: Add explicit preconditions to kasan_report()
  kasan: Make addr_has_metadata() return true for valid addresses

 include/linux/kasan.h | 7 +++++++
 mm/kasan/kasan.h      | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

-- 
2.30.0