diff options
Diffstat (limited to 'arch/x86/include/asm/uaccess.h')
| -rw-r--r-- | arch/x86/include/asm/uaccess.h | 222 |
1 files changed, 210 insertions, 12 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 5838fa911aa..0d592e0a5b8 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -40,22 +40,30 @@ /* * Test whether a block of memory is a valid user space address. * Returns 0 if the range is valid, nonzero otherwise. - * - * This is equivalent to the following test: - * (u33)addr + (u33)size > (u33)current->addr_limit.seg (u65 for x86_64) - * - * This needs 33-bit (65-bit for x86_64) arithmetic. We have a carry... */ +static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit) +{ + /* + * If we have used "sizeof()" for the size, + * we know it won't overflow the limit (but + * it might overflow the 'addr', so it's + * important to subtract the size from the + * limit, not add it to the address). + */ + if (__builtin_constant_p(size)) + return addr > limit - size; + + /* Arbitrary sizes? Be careful about overflow */ + addr += size; + if (addr < size) + return true; + return addr > limit; +} #define __range_not_ok(addr, size, limit) \ ({ \ - unsigned long flag, roksum; \ __chk_user_ptr(addr); \ - asm("add %3,%1 ; sbb %0,%0 ; cmp %1,%4 ; sbb $0,%0" \ - : "=&r" (flag), "=r" (roksum) \ - : "1" (addr), "g" ((long)(size)), \ - "rm" (limit)); \ - flag; \ + __chk_range_not_ok((unsigned long __force)(addr), size, limit); \ }) /** @@ -78,7 +86,7 @@ * this function, memory access functions may still return -EFAULT. */ #define access_ok(type, addr, size) \ - (likely(__range_not_ok(addr, size, user_addr_max()) == 0)) + likely(!__range_not_ok(addr, size, user_addr_max())) /* * The exception table consists of pairs of addresses relative to the @@ -525,6 +533,98 @@ extern __must_check long strnlen_user(const char __user *str, long n); unsigned long __must_check clear_user(void __user *mem, unsigned long len); unsigned long __must_check __clear_user(void __user *mem, unsigned long len); +extern void __cmpxchg_wrong_size(void) + __compiletime_error("Bad argument size for cmpxchg"); + +#define __user_atomic_cmpxchg_inatomic(uval, ptr, old, new, size) \ +({ \ + int __ret = 0; \ + __typeof__(ptr) __uval = (uval); \ + __typeof__(*(ptr)) __old = (old); \ + __typeof__(*(ptr)) __new = (new); \ + switch (size) { \ + case 1: \ + { \ + asm volatile("\t" ASM_STAC "\n" \ + "1:\t" LOCK_PREFIX "cmpxchgb %4, %2\n" \ + "2:\t" ASM_CLAC "\n" \ + "\t.section .fixup, \"ax\"\n" \ + "3:\tmov %3, %0\n" \ + "\tjmp 2b\n" \ + "\t.previous\n" \ + _ASM_EXTABLE(1b, 3b) \ + : "+r" (__ret), "=a" (__old), "+m" (*(ptr)) \ + : "i" (-EFAULT), "q" (__new), "1" (__old) \ + : "memory" \ + ); \ + break; \ + } \ + case 2: \ + { \ + asm volatile("\t" ASM_STAC "\n" \ + "1:\t" LOCK_PREFIX "cmpxchgw %4, %2\n" \ + "2:\t" ASM_CLAC "\n" \ + "\t.section .fixup, \"ax\"\n" \ + "3:\tmov %3, %0\n" \ + "\tjmp 2b\n" \ + "\t.previous\n" \ + _ASM_EXTABLE(1b, 3b) \ + : "+r" (__ret), "=a" (__old), "+m" (*(ptr)) \ + : "i" (-EFAULT), "r" (__new), "1" (__old) \ + : "memory" \ + ); \ + break; \ + } \ + case 4: \ + { \ + asm volatile("\t" ASM_STAC "\n" \ + "1:\t" LOCK_PREFIX "cmpxchgl %4, %2\n" \ + "2:\t" ASM_CLAC "\n" \ + "\t.section .fixup, \"ax\"\n" \ + "3:\tmov %3, %0\n" \ + "\tjmp 2b\n" \ + "\t.previous\n" \ + _ASM_EXTABLE(1b, 3b) \ + : "+r" (__ret), "=a" (__old), "+m" (*(ptr)) \ + : "i" (-EFAULT), "r" (__new), "1" (__old) \ + : "memory" \ + ); \ + break; \ + } \ + case 8: \ + { \ + if (!IS_ENABLED(CONFIG_X86_64)) \ + __cmpxchg_wrong_size(); \ + \ + asm volatile("\t" ASM_STAC "\n" \ + "1:\t" LOCK_PREFIX "cmpxchgq %4, %2\n" \ + "2:\t" ASM_CLAC "\n" \ + "\t.section .fixup, \"ax\"\n" \ + "3:\tmov %3, %0\n" \ + "\tjmp 2b\n" \ + "\t.previous\n" \ + _ASM_EXTABLE(1b, 3b) \ + : "+r" (__ret), "=a" (__old), "+m" (*(ptr)) \ + : "i" (-EFAULT), "r" (__new), "1" (__old) \ + : "memory" \ + ); \ + break; \ + } \ + default: \ + __cmpxchg_wrong_size(); \ + } \ + *__uval = __old; \ + __ret; \ +}) + +#define user_atomic_cmpxchg_inatomic(uval, ptr, old, new) \ +({ \ + access_ok(VERIFY_WRITE, (ptr), sizeof(*(ptr))) ? \ + __user_atomic_cmpxchg_inatomic((uval), (ptr), \ + (old), (new), sizeof(*(ptr))) : \ + -EFAULT; \ +}) + /* * movsl can be slow when source and dest are not both 8-byte aligned */ @@ -542,5 +642,103 @@ extern struct movsl_mask { # include <asm/uaccess_64.h> #endif +unsigned long __must_check _copy_from_user(void *to, const void __user *from, + unsigned n); +unsigned long __must_check _copy_to_user(void __user *to, const void *from, + unsigned n); + +#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS +# define copy_user_diag __compiletime_error +#else +# define copy_user_diag __compiletime_warning +#endif + +extern void copy_user_diag("copy_from_user() buffer size is too small") +copy_from_user_overflow(void); +extern void copy_user_diag("copy_to_user() buffer size is too small") +copy_to_user_overflow(void) __asm__("copy_from_user_overflow"); + +#undef copy_user_diag + +#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS + +extern void +__compiletime_warning("copy_from_user() buffer size is not provably correct") +__copy_from_user_overflow(void) __asm__("copy_from_user_overflow"); +#define __copy_from_user_overflow(size, count) __copy_from_user_overflow() + +extern void +__compiletime_warning("copy_to_user() buffer size is not provably correct") +__copy_to_user_overflow(void) __asm__("copy_from_user_overflow"); +#define __copy_to_user_overflow(size, count) __copy_to_user_overflow() + +#else + +static inline void +__copy_from_user_overflow(int size, unsigned long count) +{ + WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); +} + +#define __copy_to_user_overflow __copy_from_user_overflow + +#endif + +static inline unsigned long __must_check +copy_from_user(void *to, const void __user *from, unsigned long n) +{ + int sz = __compiletime_object_size(to); + + might_fault(); + + /* + * While we would like to have the compiler do the checking for us + * even in the non-constant size case, any false positives there are + * a problem (especially when DEBUG_STRICT_USER_COPY_CHECKS, but even + * without - the [hopefully] dangerous looking nature of the warning + * would make people go look at the respecitive call sites over and + * over again just to find that there's no problem). + * + * And there are cases where it's just not realistic for the compiler + * to prove the count to be in range. For example when multiple call + * sites of a helper function - perhaps in different source files - + * all doing proper range checking, yet the helper function not doing + * so again. + * + * Therefore limit the compile time checking to the constant size + * case, and do only runtime checking for non-constant sizes. + */ + + if (likely(sz < 0 || sz >= n)) + n = _copy_from_user(to, from, n); + else if(__builtin_constant_p(n)) + copy_from_user_overflow(); + else + __copy_from_user_overflow(sz, n); + + return n; +} + +static inline unsigned long __must_check +copy_to_user(void __user *to, const void *from, unsigned long n) +{ + int sz = __compiletime_object_size(from); + + might_fault(); + + /* See the comment in copy_from_user() above. */ + if (likely(sz < 0 || sz >= n)) + n = _copy_to_user(to, from, n); + else if(__builtin_constant_p(n)) + copy_to_user_overflow(); + else + __copy_to_user_overflow(sz, n); + + return n; +} + +#undef __copy_from_user_overflow +#undef __copy_to_user_overflow + #endif /* _ASM_X86_UACCESS_H */ |