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 <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Signed-off-by: Vincenzo Frascino <[email protected]>
---
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
On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino
<[email protected]> 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 <[email protected]>
> Cc: Alexander Potapenko <[email protected]>
> Cc: Dmitry Vyukov <[email protected]>
> Cc: Leon Romanovsky <[email protected]>
> Cc: Andrey Konovalov <[email protected]>
> Signed-off-by: Vincenzo Frascino <[email protected]>
> ---
> 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
>
On 1/22/21 2:46 PM, Andrey Konovalov wrote:
> On Fri, Jan 22, 2021 at 3:38 PM Vincenzo Frascino
> <[email protected]> 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 <[email protected]>
>> Cc: Alexander Potapenko <[email protected]>
>> Cc: Dmitry Vyukov <[email protected]>
>> Cc: Leon Romanovsky <[email protected]>
>> Cc: Andrey Konovalov <[email protected]>
>> Signed-off-by: Vincenzo Frascino <[email protected]>
>> ---
>> 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