From: Przemek Kitszel <przemyslaw.kitszel@intel.com> mainline inclusion from mainline-v6.7-rc1 commit 26dd68d293fd1c5ac966fb5dd5f6d89de322a541 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/7954 CVE: CVE-2025-39981 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Add DEFINE_FLEX() macro for on-stack allocations of structs with flexible array member. Expose __struct_size() macro outside of fortify-string.h, as it could be used to read size of structs allocated by DEFINE_FLEX(). Move __member_size() alongside it. -Kees Using underlying array for on-stack storage lets us to declare known-at-compile-time structures without kzalloc(). Actual usage for ice driver is in following patches of the series. Missing __has_builtin() workaround is moved up to serve also assembly compilation with m68k-linux-gcc, see [1]. Error was (note the .S file extension): In file included from ../include/linux/linkage.h:5, from ../arch/m68k/fpsp040/skeleton.S:40: ../include/linux/compiler_types.h:331:5: warning: "__has_builtin" is not defined, evaluates to 0 [-Wundef] 331 | #if __has_builtin(__builtin_dynamic_object_size) | ^~~~~~~~~~~~~ ../include/linux/compiler_types.h:331:18: error: missing binary operator before token "(" 331 | #if __has_builtin(__builtin_dynamic_object_size) | ^ [1] https://lore.kernel.org/netdev/202308112122.OuF0YZqL-lkp@intel.com/ Co-developed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com> Link: https://lore.kernel.org/r/20230912115937.1645707-2-przemyslaw.kitszel@intel.... Signed-off-by: Jakub Kicinski <kuba@kernel.org> Conflicts: include/linux/compiler_types.h [Context conflicts.] Signed-off-by: Jiacheng Yu <yujiacheng3@huawei.com> --- include/linux/compiler_types.h | 36 +++++++++++++++++++++++----------- include/linux/fortify-string.h | 4 ---- include/linux/overflow.h | 35 +++++++++++++++++++++++++++++++++ 3 files changed, 60 insertions(+), 15 deletions(-) diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 156d6e135c9d..3ffdb6af27ba 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -2,6 +2,15 @@ #ifndef __LINUX_COMPILER_TYPES_H #define __LINUX_COMPILER_TYPES_H +/* + * __has_builtin is supported on gcc >= 10, clang >= 3 and icc >= 21. + * In the meantime, to support gcc < 10, we implement __has_builtin + * by hand. + */ +#ifndef __has_builtin +#define __has_builtin(x) (0) +#endif + #ifndef __ASSEMBLY__ /* @@ -134,17 +143,6 @@ static inline void __chk_io_ptr(const volatile void __iomem *ptr) { } # define __preserve_most #endif -/* Builtins */ - -/* - * __has_builtin is supported on gcc >= 10, clang >= 3 and icc >= 21. - * In the meantime, to support gcc < 10, we implement __has_builtin - * by hand. - */ -#ifndef __has_builtin -#define __has_builtin(x) (0) -#endif - /* Compiler specific macros. */ #ifdef __clang__ #include <linux/compiler-clang.h> @@ -390,6 +388,18 @@ struct ftrace_likely_data { # define __realloc_size(x, ...) #endif +/* + * When the size of an allocated object is needed, use the best available + * mechanism to find it. (For cases where sizeof() cannot be used.) + */ +#if __has_builtin(__builtin_dynamic_object_size) +#define __struct_size(p) __builtin_dynamic_object_size(p, 0) +#define __member_size(p) __builtin_dynamic_object_size(p, 1) +#else +#define __struct_size(p) __builtin_object_size(p, 0) +#define __member_size(p) __builtin_object_size(p, 1) +#endif + /* * Some versions of gcc do not mark 'asm goto' volatile: * @@ -401,6 +411,10 @@ struct ftrace_likely_data { #define asm_goto_output(x...) asm volatile goto(x) #endif +#ifndef asm_volatile_goto +#define asm_volatile_goto(x...) asm goto(x) +#endif + #ifdef CONFIG_CC_HAS_ASM_INLINE #define asm_inline asm __inline #else diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index f7e1895367fa..3e4c9d0eb171 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -107,13 +107,9 @@ extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) #if __has_builtin(__builtin_dynamic_object_size) #define POS __pass_dynamic_object_size(1) #define POS0 __pass_dynamic_object_size(0) -#define __struct_size(p) __builtin_dynamic_object_size(p, 0) -#define __member_size(p) __builtin_dynamic_object_size(p, 1) #else #define POS __pass_object_size(1) #define POS0 __pass_object_size(0) -#define __struct_size(p) __builtin_object_size(p, 0) -#define __member_size(p) __builtin_object_size(p, 1) #endif #define __compiletime_lessthan(bounds, length) ( \ diff --git a/include/linux/overflow.h b/include/linux/overflow.h index e04f67947647..51af56522915 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -311,4 +311,39 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend) #define struct_size_t(type, member, count) \ struct_size((type *)NULL, member, count) +/** + * _DEFINE_FLEX() - helper macro for DEFINE_FLEX() family. + * Enables caller macro to pass (different) initializer. + * + * @type: structure type name, including "struct" keyword. + * @name: Name for a variable to define. + * @member: Name of the array member. + * @count: Number of elements in the array; must be compile-time const. + * @initializer: initializer expression (could be empty for no init). + */ +#define _DEFINE_FLEX(type, name, member, count, initializer) \ + _Static_assert(__builtin_constant_p(count), \ + "onstack flex array members require compile-time const count"); \ + union { \ + u8 bytes[struct_size_t(type, member, count)]; \ + type obj; \ + } name##_u initializer; \ + type *name = (type *)&name##_u + +/** + * DEFINE_FLEX() - Define an on-stack instance of structure with a trailing + * flexible array member. + * + * @type: structure type name, including "struct" keyword. + * @name: Name for a variable to define. + * @member: Name of the array member. + * @count: Number of elements in the array; must be compile-time const. + * + * Define a zeroed, on-stack, instance of @type structure with a trailing + * flexible array member. + * Use __struct_size(@name) to get compile-time size of it afterwards. + */ +#define DEFINE_FLEX(type, name, member, count) \ + _DEFINE_FLEX(type, name, member, count, = {}) + #endif /* __LINUX_OVERFLOW_H */ -- 2.43.0