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.) v9: Fix overflows_type() to use __builtin_add_overflow() instead of __builtin_add_overflow_p() (Andrzej) Fix overflows_ptr() to use overflows_type() with the unsigned long type (Andrzej) Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@xxxxxxxxx> Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> Cc: Matthew Auld <matthew.auld@xxxxxxxxx> Cc: Nirmoy Das <nirmoy.das@xxxxxxxxx> Cc: Jani Nikula <jani.nikula@xxxxxxxxx> Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx> Cc: Andrzej Hajda <andrzej.hajda@xxxxxxxxx> Cc: Mauro Carvalho Chehab <mauro.chehab@xxxxxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> (v5) --- drivers/gpu/drm/i915/i915_user_extensions.c | 3 +- drivers/gpu/drm/i915/i915_utils.h | 5 +- include/linux/overflow.h | 62 +++++++++++++++++++++ 3 files changed, 64 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_user_extensions.c b/drivers/gpu/drm/i915/i915_user_extensions.c index c822d0aafd2d..6f6b5b910968 100644 --- a/drivers/gpu/drm/i915/i915_user_extensions.c +++ b/drivers/gpu/drm/i915/i915_user_extensions.c @@ -50,8 +50,7 @@ int i915_user_extensions(struct i915_user_extension __user *ext, if (err) return err; - if (get_user(next, &ext->next_extension) || - overflows_type(next, ext)) + if (get_user(next, &ext->next_extension) || overflows_ptr(next)) 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..6af9df1d67a1 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -52,6 +52,68 @@ 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. Source and Destination can be different 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((x), v, &v); \ +})) + +/** + * overflows_ptr - helper for checking the occurrence of overflows when a value + * assigns to the pointer data type + * + * @x: Source value for overflow check + * + * gcc's built-in overflow check functions don't support checking between the + * pointer type and non-pointer type. And ILP32 and LP64 have the same bit size + * between long and pointer. Therefore it internally compares the source value + * and unsigned long data type for checking overflow. + * + * Returns: + * True if overflow can occur, false otherwise. + */ +#define overflows_ptr(x) __must_check_overflow(overflows_type(x, unsigned long)) + +/** + * 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