Messages in this thread | | | Date | Tue, 23 Aug 2022 14:35:38 +0200 | Subject | Re: [Intel-gfx] [PATCH v8 1/8] overflow: Move and add few utility macros into overflow | From | Andrzej Hajda <> |
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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()
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