It moves overflows_type utility macro into overflow header from i915_utils
header. The overflows_type can be used to catch the truncaion (overflow)
between different data types. And it adds check_assign() macro which
performs an assigning source value into destination ptr along with an
overflow check. overflow_type macro has been improved to handle the signbit
by gcc's built-in overflow check function. And it adds overflows_ptr()
helper macro for checking the overflows between a value and a pointer
type/value.
v3: Add is_type_unsigned() macro (Mauro)
Modify overflows_type() macro to consider signed data types (Mauro)
Fix the problem that safe_conversion() macro always returns true
v4: Fix kernel-doc markups
v6: Move macro addition location so that it can be used by other than drm
subsystem (Jani, Mauro, Andi)
Change is_type_unsigned to is_unsigned_type to have the same name form
as is_signed_type macro
v8: Add check_assign() and remove safe_conversion() (Kees)
Fix overflows_type() to use gcc's built-in overflow function (Andrzej)
Add overflows_ptr() to allow overflow checking when assigning a value
into a pointer variable (G.G.)
Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Nirmoy Das <nirmoy.das@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Mauro Carvalho Chehab <mauro.chehab@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org> (v5)
---
drivers/gpu/drm/i915/i915_user_extensions.c | 2 +-
drivers/gpu/drm/i915/i915_utils.h | 5 +-
include/linux/overflow.h | 67 +++++++++++++++++++++
3 files changed, 69 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_user_extensions.c b/drivers/gpu/drm/i915/i915_user_extensions.c
index c822d0aafd2d..0fb2fecbcaae 100644
--- a/drivers/gpu/drm/i915/i915_user_extensions.c
+++ b/drivers/gpu/drm/i915/i915_user_extensions.c
@@ -51,7 +51,7 @@ int i915_user_extensions(struct i915_user_extension __user *ext,
return err;
if (get_user(next, &ext->next_extension) ||
- overflows_type(next, ext))
+ overflows_ptr(next, ext))
return -EFAULT;
ext = u64_to_user_ptr(next);
diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
index c10d68cdc3ca..eb0ded23fa9c 100644
--- a/drivers/gpu/drm/i915/i915_utils.h
+++ b/drivers/gpu/drm/i915/i915_utils.h
@@ -32,6 +32,7 @@
#include <linux/types.h>
#include <linux/workqueue.h>
#include <linux/sched/clock.h>
+#include <linux/overflow.h>
#ifdef CONFIG_X86
#include <asm/hypervisor.h>
@@ -111,10 +112,6 @@ bool i915_error_injected(void);
#define range_overflows_end_t(type, start, size, max) \
range_overflows_end((type)(start), (type)(size), (type)(max))
-/* Note we don't consider signbits :| */
-#define overflows_type(x, T) \
- (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T))
-
#define ptr_mask_bits(ptr, n) ({ \
unsigned long __v = (unsigned long)(ptr); \
(typeof(ptr))(__v & -BIT(n)); \
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index f1221d11f8e5..4016f1378bcc 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -52,6 +52,73 @@ static inline bool __must_check __must_check_overflow(bool overflow)
return unlikely(overflow);
}
+/**
+ * overflows_type - helper for checking the overflows between data types or
+ * values
+ *
+ * @x: Source value or data type for overflow check
+ * @T: Destination value or data type for overflow check
+ *
+ * It compares the values or data type between the first and second argument to
+ * check whether overflow can occur when assigning the first argument to the
+ * variable of the second argument. Source and Destination can be singned or
+ * unsigned data types.
+ *
+ * Returns:
+ * True if overflow can occur, false otherwise.
+ */
+#define overflows_type(x, T) __must_check_overflow(({ \
+ typeof(T) v = 0; \
+ __builtin_add_overflow_p((x), v, v); \
+}))
+
+/**
+ * overflows_ptr - helper for checking the overflows between a value and
+ * a pointer type/value
+ *
+ * @x: Source value for overflow check
+ * @T: Destination pointer type or value for overflow check
+ *
+ * gcc's built-in overflow check functions don't support checking between the
+ * pointer type and non-pointer type. Therefore it compares the values and
+ * size of each data type between the first and second argument to check whether
+ * truncation can occur when assigning the first argument to the variable of the
+ * second argument. It checks internally the ptr is a pointer type.
+ *
+ * Returns:
+ * True if overflow can occur, false otherwise.
+ */
+#define overflows_ptr(x, T) __must_check_overflow(({ \
+ typecheck_pointer(T); \
+ ((x) < 0) ? 1 : (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T)) ? 1 : 0; \
+}))
+
+/**
+ * check_assign - perform an assigning source value into destination ptr along
+ * with an overflow check.
+ *
+ * @value: Source value
+ * @ptr: Destination pointer address, If the pointer type is not used,
+ * a warning message is output during build.
+ *
+ * It checks internally the ptr is a pointer type. And it uses gcc's built-in
+ * overflow check function.
+ * It does not use the check_*() wrapper functions, but directly uses gcc's
+ * built-in overflow check function so that it can be used even when
+ * the type of value and the type pointed to by ptr are different without build
+ * warning messages.
+ *
+ * Returns:
+ * If the value would overflow the destination, it returns true. If not return
+ * false. When overflow does not occur, the assigning into ptr from value
+ * succeeds. It follows the return policy as other check_*_overflow() functions
+ * return non-zero as a failure.
+ */
+#define check_assign(value, ptr) __must_check_overflow(({ \
+ typecheck_pointer(ptr); \
+ __builtin_add_overflow(0, value, ptr); \
+}))
+
/*
* For simplicity and code hygiene, the fallback code below insists on
* a, b and *d having the same type (similar to the min() and max()
--
2.37.1
On 23.08.2022 12:17, Gwan-gyeong Mun wrote:
> It moves overflows_type utility macro into overflow header from i915_utils
> header. The overflows_type can be used to catch the truncaion (overflow)
> between different data types. And it adds check_assign() macro which
> performs an assigning source value into destination ptr along with an
> overflow check. overflow_type macro has been improved to handle the signbit
> by gcc's built-in overflow check function. And it adds overflows_ptr()
> helper macro for checking the overflows between a value and a pointer
> type/value.
>
> v3: Add is_type_unsigned() macro (Mauro)
> Modify overflows_type() macro to consider signed data types (Mauro)
> Fix the problem that safe_conversion() macro always returns true
> v4: Fix kernel-doc markups
> v6: Move macro addition location so that it can be used by other than drm
> subsystem (Jani, Mauro, Andi)
> Change is_type_unsigned to is_unsigned_type to have the same name form
> as is_signed_type macro
> v8: Add check_assign() and remove safe_conversion() (Kees)
> Fix overflows_type() to use gcc's built-in overflow function (Andrzej)
> Add overflows_ptr() to allow overflow checking when assigning a value
> into a pointer variable (G.G.)
>
> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Nirmoy Das <nirmoy.das@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: Andrzej Hajda <andrzej.hajda@intel.com>
> Cc: Mauro Carvalho Chehab <mauro.chehab@linux.intel.com>
> Cc: Kees Cook <keescook@chromium.org>
> Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org> (v5)
> ---
> drivers/gpu/drm/i915/i915_user_extensions.c | 2 +-
> drivers/gpu/drm/i915/i915_utils.h | 5 +-
> include/linux/overflow.h | 67 +++++++++++++++++++++
> 3 files changed, 69 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_user_extensions.c b/drivers/gpu/drm/i915/i915_user_extensions.c
> index c822d0aafd2d..0fb2fecbcaae 100644
> --- a/drivers/gpu/drm/i915/i915_user_extensions.c
> +++ b/drivers/gpu/drm/i915/i915_user_extensions.c
> @@ -51,7 +51,7 @@ int i915_user_extensions(struct i915_user_extension __user *ext,
> return err;
>
> if (get_user(next, &ext->next_extension) ||
> - overflows_type(next, ext))
> + overflows_ptr(next, ext))
> return -EFAULT;
>
> ext = u64_to_user_ptr(next);
> diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
> index c10d68cdc3ca..eb0ded23fa9c 100644
> --- a/drivers/gpu/drm/i915/i915_utils.h
> +++ b/drivers/gpu/drm/i915/i915_utils.h
> @@ -32,6 +32,7 @@
> #include <linux/types.h>
> #include <linux/workqueue.h>
> #include <linux/sched/clock.h>
> +#include <linux/overflow.h>
>
> #ifdef CONFIG_X86
> #include <asm/hypervisor.h>
> @@ -111,10 +112,6 @@ bool i915_error_injected(void);
> #define range_overflows_end_t(type, start, size, max) \
> range_overflows_end((type)(start), (type)(size), (type)(max))
>
> -/* Note we don't consider signbits :| */
> -#define overflows_type(x, T) \
> - (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T))
> -
> #define ptr_mask_bits(ptr, n) ({ \
> unsigned long __v = (unsigned long)(ptr); \
> (typeof(ptr))(__v & -BIT(n)); \
> diff --git a/include/linux/overflow.h b/include/linux/overflow.h
> index f1221d11f8e5..4016f1378bcc 100644
> --- a/include/linux/overflow.h
> +++ b/include/linux/overflow.h
> @@ -52,6 +52,73 @@ static inline bool __must_check __must_check_overflow(bool overflow)
> return unlikely(overflow);
> }
>
> +/**
> + * overflows_type - helper for checking the overflows between data types or
> + * values
> + *
> + * @x: Source value or data type for overflow check
> + * @T: Destination value or data type for overflow check
> + *
> + * It compares the values or data type between the first and second argument to
> + * check whether overflow can occur when assigning the first argument to the
> + * variable of the second argument. Source and Destination can be singned or
> + * unsigned data types.
> + *
> + * Returns:
> + * True if overflow can occur, false otherwise.
> + */
> +#define overflows_type(x, T) __must_check_overflow(({ \
> + typeof(T) v = 0; \
> + __builtin_add_overflow_p((x), v, v); \
Above works since gcc7, since gcc5 you can use:
__builtin_add_overflow((x), v, &v);
> +}))
> +
> +/**
> + * overflows_ptr - helper for checking the overflows between a value and
> + * a pointer type/value
> + *
> + * @x: Source value for overflow check
> + * @T: Destination pointer type or value for overflow check
> + *
> + * gcc's built-in overflow check functions don't support checking between the
> + * pointer type and non-pointer type. Therefore it compares the values and
> + * size of each data type between the first and second argument to check whether
> + * truncation can occur when assigning the first argument to the variable of the
> + * second argument. It checks internally the ptr is a pointer type.
> + *
> + * Returns:
> + * True if overflow can occur, false otherwise.
> + */
> +#define overflows_ptr(x, T) __must_check_overflow(({ \
> + typecheck_pointer(T); \
> + ((x) < 0) ? 1 : (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T)) ? 1 : 0; \
> +}))
Doesn't linux assume that all pointers have size of long int ?
Or at least all pointers have the same size.
In such case we can use:
#define overflows_ptr(x) overflows_type(x, unsigned long)
Regards
Andrzej
> +
> +/**
> + * check_assign - perform an assigning source value into destination ptr along
> + * with an overflow check.
> + *
> + * @value: Source value
> + * @ptr: Destination pointer address, If the pointer type is not used,
> + * a warning message is output during build.
> + *
> + * It checks internally the ptr is a pointer type. And it uses gcc's built-in
> + * overflow check function.
> + * It does not use the check_*() wrapper functions, but directly uses gcc's
> + * built-in overflow check function so that it can be used even when
> + * the type of value and the type pointed to by ptr are different without build
> + * warning messages.
> + *
> + * Returns:
> + * If the value would overflow the destination, it returns true. If not return
> + * false. When overflow does not occur, the assigning into ptr from value
> + * succeeds. It follows the return policy as other check_*_overflow() functions
> + * return non-zero as a failure.
> + */
> +#define check_assign(value, ptr) __must_check_overflow(({ \
> + typecheck_pointer(ptr); \
> + __builtin_add_overflow(0, value, ptr); \
> +}))
> +
> /*
> * For simplicity and code hygiene, the fallback code below insists on
> * a, b and *d having the same type (similar to the min() and max()
On 8/23/22 9:35 PM, Andrzej Hajda wrote:
> On 23.08.2022 12:17, Gwan-gyeong Mun wrote:
>> It moves overflows_type utility macro into overflow header from
>> i915_utils
>> header. The overflows_type can be used to catch the truncaion (overflow)
>> between different data types. And it adds check_assign() macro which
>> performs an assigning source value into destination ptr along with an
>> overflow check. overflow_type macro has been improved to handle the
>> signbit
>> by gcc's built-in overflow check function. And it adds overflows_ptr()
>> helper macro for checking the overflows between a value and a pointer
>> type/value.
>>
>> v3: Add is_type_unsigned() macro (Mauro)
>> Modify overflows_type() macro to consider signed data types (Mauro)
>> Fix the problem that safe_conversion() macro always returns true
>> v4: Fix kernel-doc markups
>> v6: Move macro addition location so that it can be used by other than drm
>> subsystem (Jani, Mauro, Andi)
>> Change is_type_unsigned to is_unsigned_type to have the same name
>> form
>> as is_signed_type macro
>> v8: Add check_assign() and remove safe_conversion() (Kees)
>> Fix overflows_type() to use gcc's built-in overflow function
>> (Andrzej)
>> Add overflows_ptr() to allow overflow checking when assigning a
>> value
>> into a pointer variable (G.G.)
>>
>> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
>> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>> Cc: Matthew Auld <matthew.auld@intel.com>
>> Cc: Nirmoy Das <nirmoy.das@intel.com>
>> Cc: Jani Nikula <jani.nikula@intel.com>
>> Cc: Andi Shyti <andi.shyti@linux.intel.com>
>> Cc: Andrzej Hajda <andrzej.hajda@intel.com>
>> Cc: Mauro Carvalho Chehab <mauro.chehab@linux.intel.com>
>> Cc: Kees Cook <keescook@chromium.org>
>> Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org> (v5)
>> ---
>> drivers/gpu/drm/i915/i915_user_extensions.c | 2 +-
>> drivers/gpu/drm/i915/i915_utils.h | 5 +-
>> include/linux/overflow.h | 67 +++++++++++++++++++++
>> 3 files changed, 69 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_user_extensions.c
>> b/drivers/gpu/drm/i915/i915_user_extensions.c
>> index c822d0aafd2d..0fb2fecbcaae 100644
>> --- a/drivers/gpu/drm/i915/i915_user_extensions.c
>> +++ b/drivers/gpu/drm/i915/i915_user_extensions.c
>> @@ -51,7 +51,7 @@ int i915_user_extensions(struct i915_user_extension
>> __user *ext,
>> return err;
>> if (get_user(next, &ext->next_extension) ||
>> - overflows_type(next, ext))
>> + overflows_ptr(next, ext))
>> return -EFAULT;
>> ext = u64_to_user_ptr(next);
>> diff --git a/drivers/gpu/drm/i915/i915_utils.h
>> b/drivers/gpu/drm/i915/i915_utils.h
>> index c10d68cdc3ca..eb0ded23fa9c 100644
>> --- a/drivers/gpu/drm/i915/i915_utils.h
>> +++ b/drivers/gpu/drm/i915/i915_utils.h
>> @@ -32,6 +32,7 @@
>> #include <linux/types.h>
>> #include <linux/workqueue.h>
>> #include <linux/sched/clock.h>
>> +#include <linux/overflow.h>
>> #ifdef CONFIG_X86
>> #include <asm/hypervisor.h>
>> @@ -111,10 +112,6 @@ bool i915_error_injected(void);
>> #define range_overflows_end_t(type, start, size, max) \
>> range_overflows_end((type)(start), (type)(size), (type)(max))
>> -/* Note we don't consider signbits :| */
>> -#define overflows_type(x, T) \
>> - (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T))
>> -
>> #define ptr_mask_bits(ptr, n) ({ \
>> unsigned long __v = (unsigned long)(ptr); \
>> (typeof(ptr))(__v & -BIT(n)); \
>> diff --git a/include/linux/overflow.h b/include/linux/overflow.h
>> index f1221d11f8e5..4016f1378bcc 100644
>> --- a/include/linux/overflow.h
>> +++ b/include/linux/overflow.h
>> @@ -52,6 +52,73 @@ static inline bool __must_check
>> __must_check_overflow(bool overflow)
>> return unlikely(overflow);
>> }
>> +/**
>> + * overflows_type - helper for checking the overflows between data
>> types or
>> + * values
>> + *
>> + * @x: Source value or data type for overflow check
>> + * @T: Destination value or data type for overflow check
>> + *
>> + * It compares the values or data type between the first and second
>> argument to
>> + * check whether overflow can occur when assigning the first argument
>> to the
>> + * variable of the second argument. Source and Destination can be
>> singned or
>> + * unsigned data types.
>> + *
>> + * Returns:
>> + * True if overflow can occur, false otherwise.
>> + */
>> +#define overflows_type(x, T) __must_check_overflow(({ \
>> + typeof(T) v = 0; \
>> + __builtin_add_overflow_p((x), v, v); \
>
>
> Above works since gcc7, since gcc5 you can use:
> __builtin_add_overflow((x), v, &v);
>
Yes I'll update it to use __builtin_add_overflow() like where the gcc's
overflow check built-in function was used.
>
>> +}))
>> +
>> +/**
>> + * overflows_ptr - helper for checking the overflows between a value and
>> + * a pointer type/value
>> + *
>> + * @x: Source value for overflow check
>> + * @T: Destination pointer type or value for overflow check
>> + *
>> + * gcc's built-in overflow check functions don't support checking
>> between the
>> + * pointer type and non-pointer type. Therefore it compares the
>> values and
>> + * size of each data type between the first and second argument to
>> check whether
>> + * truncation can occur when assigning the first argument to the
>> variable of the
>> + * second argument. It checks internally the ptr is a pointer type.
>> + *
>> + * Returns:
>> + * True if overflow can occur, false otherwise.
>> + */
>> +#define overflows_ptr(x, T) __must_check_overflow(({ \
>> + typecheck_pointer(T); \
>> + ((x) < 0) ? 1 : (sizeof(x) > sizeof(T) && (x) >>
>> BITS_PER_TYPE(T)) ? 1 : 0; \
>> +}))
>
>
> Doesn't linux assume that all pointers have size of long int ?
> Or at least all pointers have the same size.
> In such case we can use:
> #define overflows_ptr(x) overflows_type(x, unsigned long)
>
yes it looks a better way. I'll update the macro and comments.
Thanks Andrzej
G.G.
> Regards
> Andrzej
>
>> +
>> +/**
>> + * check_assign - perform an assigning source value into destination
>> ptr along
>> + * with an overflow check.
>> + *
>> + * @value: Source value
>> + * @ptr: Destination pointer address, If the pointer type is not used,
>> + * a warning message is output during build.
>> + *
>> + * It checks internally the ptr is a pointer type. And it uses gcc's
>> built-in
>> + * overflow check function.
>> + * It does not use the check_*() wrapper functions, but directly uses
>> gcc's
>> + * built-in overflow check function so that it can be used even when
>> + * the type of value and the type pointed to by ptr are different
>> without build
>> + * warning messages.
>> + *
>> + * Returns:
>> + * If the value would overflow the destination, it returns true. If
>> not return
>> + * false. When overflow does not occur, the assigning into ptr from
>> value
>> + * succeeds. It follows the return policy as other check_*_overflow()
>> functions
>> + * return non-zero as a failure.
>> + */
>> +#define check_assign(value, ptr) __must_check_overflow(({ \
>> + typecheck_pointer(ptr); \
>> + __builtin_add_overflow(0, value, ptr); \
>> +}))
>> +
>> /*
>> * For simplicity and code hygiene, the fallback code below insists on
>> * a, b and *d having the same type (similar to the min() and max()
>
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