[PATCH v3 0/2] kasan: Fix metadata detection for KASAN_HW_TAGS

[PATCH v3 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: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

Vincenzo Frascino (2):
  arm64: Improve kernel address detection of __is_lm_address()
  kasan: Add explicit preconditions to kasan_report()

 arch/arm64/include/asm/memory.h | 6 ++++--
 include/linux/kasan.h           | 7 +++++++
 mm/kasan/kasan.h                | 2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

-- 
2.30.0

[PATCH v3 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: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

Vincenzo Frascino (2):
  arm64: Improve kernel address detection of __is_lm_address()
  kasan: Add explicit preconditions to kasan_report()

 arch/arm64/include/asm/memory.h | 6 ++++--
 include/linux/kasan.h           | 7 +++++++
 mm/kasan/kasan.h                | 2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

-- 
2.30.0


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[PATCH v3 1/2] arm64: Improve kernel address detection of __is_lm_address()

[Vincenzo Frascino]

Currently, the __is_lm_address() check just masks out the top 12 bits
of the address, but if they are 0, it still yields a true result.
This has as a side effect that virt_addr_valid() returns true even for
invalid virtual addresses (e.g. 0x0).

Improve the detection checking that it's actually a kernel address
starting at PAGE_OFFSET.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 arch/arm64/include/asm/memory.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 18fce223b67b..99d7e1494aaa 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -247,9 +247,11 @@ static inline const void *__tag_set(const void *addr, u8 tag)
 
 
 /*
- * The linear kernel range starts at the bottom of the virtual address space.
+ * Check whether an arbitrary address is within the linear map, which
+ * lives in the [PAGE_OFFSET, PAGE_END) interval at the bottom of the
+ * kernel's TTBR1 address range.
  */
-#define __is_lm_address(addr)	(((u64)(addr) & ~PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET))
+#define __is_lm_address(addr)	(((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET))
 
 #define __lm_to_phys(addr)	(((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)
 #define __kimg_to_phys(addr)	((addr) - kimage_voffset)
-- 
2.30.0

[PATCH v3 1/2] arm64: Improve kernel address detection of __is_lm_address()

[Vincenzo Frascino]

Currently, the __is_lm_address() check just masks out the top 12 bits
of the address, but if they are 0, it still yields a true result.
This has as a side effect that virt_addr_valid() returns true even for
invalid virtual addresses (e.g. 0x0).

Improve the detection checking that it's actually a kernel address
starting at PAGE_OFFSET.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 arch/arm64/include/asm/memory.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 18fce223b67b..99d7e1494aaa 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -247,9 +247,11 @@ static inline const void *__tag_set(const void *addr, u8 tag)
 
 
 /*
- * The linear kernel range starts at the bottom of the virtual address space.
+ * Check whether an arbitrary address is within the linear map, which
+ * lives in the [PAGE_OFFSET, PAGE_END) interval at the bottom of the
+ * kernel's TTBR1 address range.
  */
-#define __is_lm_address(addr)	(((u64)(addr) & ~PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET))
+#define __is_lm_address(addr)	(((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET))
 
 #define __lm_to_phys(addr)	(((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)
 #define __kimg_to_phys(addr)	((addr) - kimage_voffset)
-- 
2.30.0


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[PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report()

[Vincenzo Frascino]

With the introduction of KASAN_HW_TAGS, kasan_report() dereferences
the address passed as a parameter.

Add a comment to make sure that the preconditions to the function are
explicitly clarified.

Note: An invalid address (e.g. NULL) passed to the function when,
KASAN_HW_TAGS is enabled, leads to a kernel panic.

Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 include/linux/kasan.h | 7 +++++++
 mm/kasan/kasan.h      | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index fe1ae73ff8b5..0aea9e2a2a01 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr)
 	return (void *)arch_kasan_reset_tag(addr);
 }
 
+/**
+ * kasan_report - print a report about a bad memory access detected by KASAN
+ * @addr: address of the bad access
+ * @size: size of the bad access
+ * @is_write: whether the bad access is a write or a read
+ * @ip: instruction pointer for the accessibility check or the bad access itself
+ */
 bool kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index cc4d9e1d49b1..8c706e7652f2 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
 
 static inline bool addr_has_metadata(const void *addr)
 {
-	return true;
+	return (is_vmalloc_addr(addr) || virt_addr_valid(addr));
 }
 
 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
-- 
2.30.0

[PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report()

[Vincenzo Frascino]

With the introduction of KASAN_HW_TAGS, kasan_report() dereferences
the address passed as a parameter.

Add a comment to make sure that the preconditions to the function are
explicitly clarified.

Note: An invalid address (e.g. NULL) passed to the function when,
KASAN_HW_TAGS is enabled, leads to a kernel panic.

Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 include/linux/kasan.h | 7 +++++++
 mm/kasan/kasan.h      | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index fe1ae73ff8b5..0aea9e2a2a01 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr)
 	return (void *)arch_kasan_reset_tag(addr);
 }
 
+/**
+ * kasan_report - print a report about a bad memory access detected by KASAN
+ * @addr: address of the bad access
+ * @size: size of the bad access
+ * @is_write: whether the bad access is a write or a read
+ * @ip: instruction pointer for the accessibility check or the bad access itself
+ */
 bool kasan_report(unsigned long addr, size_t size,
 		bool is_write, unsigned long ip);
 
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index cc4d9e1d49b1..8c706e7652f2 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
 
 static inline bool addr_has_metadata(const void *addr)
 {
-	return true;
+	return (is_vmalloc_addr(addr) || virt_addr_valid(addr));
 }
 
 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
-- 
2.30.0


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Re: [PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report()

[Andrey Konovalov]

On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> With the introduction of KASAN_HW_TAGS, kasan_report() dereferences
> the address passed as a parameter.

It doesn't dereference the address, it accesses the metadata. And only
when addr_has_metadata() succeeds.

>
> Add a comment to make sure that the preconditions to the function are
> explicitly clarified.
>
> Note: An invalid address (e.g. NULL) passed to the function when,
> KASAN_HW_TAGS is enabled, leads to a kernel panic.

This is no longer true, right? Commit description needs to be updated.

>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Leon Romanovsky <leonro@mellanox.com>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
>  include/linux/kasan.h | 7 +++++++
>  mm/kasan/kasan.h      | 2 +-
>  2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index fe1ae73ff8b5..0aea9e2a2a01 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr)
>         return (void *)arch_kasan_reset_tag(addr);
>  }
>
> +/**
> + * kasan_report - print a report about a bad memory access detected by KASAN
> + * @addr: address of the bad access
> + * @size: size of the bad access
> + * @is_write: whether the bad access is a write or a read
> + * @ip: instruction pointer for the accessibility check or the bad access itself
> + */

Looks good, thanks!

>  bool kasan_report(unsigned long addr, size_t size,
>                 bool is_write, unsigned long ip);
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index cc4d9e1d49b1..8c706e7652f2 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
>
>  static inline bool addr_has_metadata(const void *addr)
>  {
> -       return true;
> +       return (is_vmalloc_addr(addr) || virt_addr_valid(addr));
>  }

Let's put this change into a separate patch.

>
>  #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
> --
> 2.30.0
>

Re: [PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report()

[Andrey Konovalov]

On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> With the introduction of KASAN_HW_TAGS, kasan_report() dereferences
> the address passed as a parameter.

It doesn't dereference the address, it accesses the metadata. And only
when addr_has_metadata() succeeds.

>
> Add a comment to make sure that the preconditions to the function are
> explicitly clarified.
>
> Note: An invalid address (e.g. NULL) passed to the function when,
> KASAN_HW_TAGS is enabled, leads to a kernel panic.

This is no longer true, right? Commit description needs to be updated.

>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Leon Romanovsky <leonro@mellanox.com>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
>  include/linux/kasan.h | 7 +++++++
>  mm/kasan/kasan.h      | 2 +-
>  2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index fe1ae73ff8b5..0aea9e2a2a01 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr)
>         return (void *)arch_kasan_reset_tag(addr);
>  }
>
> +/**
> + * kasan_report - print a report about a bad memory access detected by KASAN
> + * @addr: address of the bad access
> + * @size: size of the bad access
> + * @is_write: whether the bad access is a write or a read
> + * @ip: instruction pointer for the accessibility check or the bad access itself
> + */

Looks good, thanks!

>  bool kasan_report(unsigned long addr, size_t size,
>                 bool is_write, unsigned long ip);
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index cc4d9e1d49b1..8c706e7652f2 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
>
>  static inline bool addr_has_metadata(const void *addr)
>  {
> -       return true;
> +       return (is_vmalloc_addr(addr) || virt_addr_valid(addr));
>  }

Let's put this change into a separate patch.

>
>  #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
> --
> 2.30.0
>

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Re: [PATCH v3 1/2] arm64: Improve kernel address detection of __is_lm_address()

[Catalin Marinas]

On Fri, Jan 22, 2021 at 02:37:47PM +0000, Vincenzo Frascino wrote:
> Currently, the __is_lm_address() check just masks out the top 12 bits
> of the address, but if they are 0, it still yields a true result.
> This has as a side effect that virt_addr_valid() returns true even for
> invalid virtual addresses (e.g. 0x0).
> 
> Improve the detection checking that it's actually a kernel address
> starting at PAGE_OFFSET.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

The question is whether we leave this for 5.12 or we merge it earlier.

-- 
Catalin

Re: [PATCH v3 1/2] arm64: Improve kernel address detection of __is_lm_address()

[Catalin Marinas]

On Fri, Jan 22, 2021 at 02:37:47PM +0000, Vincenzo Frascino wrote:
> Currently, the __is_lm_address() check just masks out the top 12 bits
> of the address, but if they are 0, it still yields a true result.
> This has as a side effect that virt_addr_valid() returns true even for
> invalid virtual addresses (e.g. 0x0).
> 
> Improve the detection checking that it's actually a kernel address
> starting at PAGE_OFFSET.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

The question is whether we leave this for 5.12 or we merge it earlier.

-- 
Catalin

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Re: [PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report()

[Vincenzo Frascino]

On 1/22/21 2:46 PM, Andrey Konovalov wrote:
> On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino
> <vincenzo.frascino@arm.com> wrote:
>>
>> With the introduction of KASAN_HW_TAGS, kasan_report() dereferences
>> the address passed as a parameter.
> 
> It doesn't dereference the address, it accesses the metadata. And only
> when addr_has_metadata() succeeds.
>

Yes, this is correct. Seems I forgot again to unstash something. Will fix it in v4.

>>
>> Add a comment to make sure that the preconditions to the function are
>> explicitly clarified.
>>
>> Note: An invalid address (e.g. NULL) passed to the function when,
>> KASAN_HW_TAGS is enabled, leads to a kernel panic.
> 
> This is no longer true, right? Commit description needs to be updated.
> 
>>
>> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> Cc: Alexander Potapenko <glider@google.com>
>> Cc: Dmitry Vyukov <dvyukov@google.com>
>> Cc: Leon Romanovsky <leonro@mellanox.com>
>> Cc: Andrey Konovalov <andreyknvl@google.com>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> ---
>>  include/linux/kasan.h | 7 +++++++
>>  mm/kasan/kasan.h      | 2 +-
>>  2 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
>> index fe1ae73ff8b5..0aea9e2a2a01 100644
>> --- a/include/linux/kasan.h
>> +++ b/include/linux/kasan.h
>> @@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr)
>>         return (void *)arch_kasan_reset_tag(addr);
>>  }
>>
>> +/**
>> + * kasan_report - print a report about a bad memory access detected by KASAN
>> + * @addr: address of the bad access
>> + * @size: size of the bad access
>> + * @is_write: whether the bad access is a write or a read
>> + * @ip: instruction pointer for the accessibility check or the bad access itself
>> + */
> 
> Looks good, thanks!
> 
>>  bool kasan_report(unsigned long addr, size_t size,
>>                 bool is_write, unsigned long ip);
>>
>> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
>> index cc4d9e1d49b1..8c706e7652f2 100644
>> --- a/mm/kasan/kasan.h
>> +++ b/mm/kasan/kasan.h
>> @@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
>>
>>  static inline bool addr_has_metadata(const void *addr)
>>  {
>> -       return true;
>> +       return (is_vmalloc_addr(addr) || virt_addr_valid(addr));
>>  }
> 
> Let's put this change into a separate patch.
>

Ok, it will be done in v4.

>>
>>  #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
>> --
>> 2.30.0
>>

-- 
Regards,
Vincenzo

Re: [PATCH v3 2/2] kasan: Add explicit preconditions to kasan_report()

[Vincenzo Frascino]

On 1/22/21 2:46 PM, Andrey Konovalov wrote:
> On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino
> <vincenzo.frascino@arm.com> wrote:
>>
>> With the introduction of KASAN_HW_TAGS, kasan_report() dereferences
>> the address passed as a parameter.
> 
> It doesn't dereference the address, it accesses the metadata. And only
> when addr_has_metadata() succeeds.
>

Yes, this is correct. Seems I forgot again to unstash something. Will fix it in v4.

>>
>> Add a comment to make sure that the preconditions to the function are
>> explicitly clarified.
>>
>> Note: An invalid address (e.g. NULL) passed to the function when,
>> KASAN_HW_TAGS is enabled, leads to a kernel panic.
> 
> This is no longer true, right? Commit description needs to be updated.
> 
>>
>> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> Cc: Alexander Potapenko <glider@google.com>
>> Cc: Dmitry Vyukov <dvyukov@google.com>
>> Cc: Leon Romanovsky <leonro@mellanox.com>
>> Cc: Andrey Konovalov <andreyknvl@google.com>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> ---
>>  include/linux/kasan.h | 7 +++++++
>>  mm/kasan/kasan.h      | 2 +-
>>  2 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
>> index fe1ae73ff8b5..0aea9e2a2a01 100644
>> --- a/include/linux/kasan.h
>> +++ b/include/linux/kasan.h
>> @@ -333,6 +333,13 @@ static inline void *kasan_reset_tag(const void *addr)
>>         return (void *)arch_kasan_reset_tag(addr);
>>  }
>>
>> +/**
>> + * kasan_report - print a report about a bad memory access detected by KASAN
>> + * @addr: address of the bad access
>> + * @size: size of the bad access
>> + * @is_write: whether the bad access is a write or a read
>> + * @ip: instruction pointer for the accessibility check or the bad access itself
>> + */
> 
> Looks good, thanks!
> 
>>  bool kasan_report(unsigned long addr, size_t size,
>>                 bool is_write, unsigned long ip);
>>
>> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
>> index cc4d9e1d49b1..8c706e7652f2 100644
>> --- a/mm/kasan/kasan.h
>> +++ b/mm/kasan/kasan.h
>> @@ -209,7 +209,7 @@ bool check_memory_region(unsigned long addr, size_t size, bool write,
>>
>>  static inline bool addr_has_metadata(const void *addr)
>>  {
>> -       return true;
>> +       return (is_vmalloc_addr(addr) || virt_addr_valid(addr));
>>  }
> 
> Let's put this change into a separate patch.
>

Ok, it will be done in v4.

>>
>>  #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
>> --
>> 2.30.0
>>

-- 
Regards,
Vincenzo

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