From d597580d373774b1bdab84b3d26ff0b55162b916 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 20 Mar 2017 21:56:06 -0400 Subject: generic ...copy_..._user primitives provide raw_copy_..._user() and select ARCH_HAS_RAW_COPY_USER to use those. Signed-off-by: Al Viro --- arch/Kconfig | 3 + include/asm-generic/uaccess.h | 11 +++ include/linux/uaccess.h | 187 ++++++++++++++++++++++++++++++++++++++++++ lib/Makefile | 2 + lib/usercopy.c | 26 ++++++ 5 files changed, 229 insertions(+) create mode 100644 lib/usercopy.c diff --git a/arch/Kconfig b/arch/Kconfig index cd211a14a88f..315d37626ddc 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -847,4 +847,7 @@ config STRICT_MODULE_RWX config ARCH_WANT_RELAX_ORDER bool +config ARCH_HAS_RAW_COPY_USER + bool + source "kernel/gcov/Kconfig" diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h index bd7a05e9582b..d65c311eb128 100644 --- a/include/asm-generic/uaccess.h +++ b/include/asm-generic/uaccess.h @@ -86,7 +86,11 @@ static inline int __access_ok(unsigned long addr, unsigned long size) static inline int __put_user_fn(size_t size, void __user *ptr, void *x) { +#ifdef CONFIG_ARCH_HAS_RAW_COPY_USER + return unlikely(raw_copy_to_user(ptr, x, size)) ? -EFAULT : 0; +#else return unlikely(__copy_to_user(ptr, x, size)) ? -EFAULT : 0; +#endif } #define __put_user_fn(sz, u, k) __put_user_fn(sz, u, k) @@ -147,7 +151,11 @@ extern int __put_user_bad(void) __attribute__((noreturn)); #ifndef __get_user_fn static inline int __get_user_fn(size_t size, const void __user *ptr, void *x) { +#ifdef CONFIG_ARCH_HAS_RAW_COPY_USER + return unlikely(raw_copy_from_user(x, ptr, size)) ? -EFAULT : 0; +#else return unlikely(__copy_from_user(x, ptr, size)) ? -EFAULT : 0; +#endif } #define __get_user_fn(sz, u, k) __get_user_fn(sz, u, k) @@ -156,6 +164,8 @@ static inline int __get_user_fn(size_t size, const void __user *ptr, void *x) extern int __get_user_bad(void) __attribute__((noreturn)); +#ifndef CONFIG_ARCH_HAS_RAW_COPY_USER + #ifndef __copy_from_user_inatomic #define __copy_from_user_inatomic __copy_from_user #endif @@ -185,6 +195,7 @@ static inline long copy_to_user(void __user *to, else return n; } +#endif /* * Copy a null terminated string from userspace. diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 9c3ae8706e9d..5f76bc995d96 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -3,6 +3,7 @@ #include #include +#include #define VERIFY_READ 0 #define VERIFY_WRITE 1 @@ -11,6 +12,192 @@ #include +#ifdef CONFIG_ARCH_HAS_RAW_COPY_USER +/* + * Architectures should provide two primitives (raw_copy_{to,from}_user()) + * select ARCH_HAS_RAW_COPY_FROM_USER and get rid of their private instances + * of copy_{to,from}_user() and __copy_{to,from}_user{,_inatomic}(). Once + * all of them switch, this part of linux/uaccess.h will become unconditional. + * + * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and + * return the amount left to copy. They should assume that access_ok() has + * already been checked (and succeeded); they should *not* zero-pad anything. + * No KASAN or object size checks either - those belong here. + * + * Both of these functions should attempt to copy size bytes starting at from + * into the area starting at to. They must not fetch or store anything + * outside of those areas. Return value must be between 0 (everything + * copied successfully) and size (nothing copied). + * + * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting + * at to must become equal to the bytes fetched from the corresponding area + * starting at from. All data past to + size - N must be left unmodified. + * + * If copying succeeds, the return value must be 0. If some data cannot be + * fetched, it is permitted to copy less than had been fetched; the only + * hard requirement is that not storing anything at all (i.e. returning size) + * should happen only when nothing could be copied. In other words, you don't + * have to squeeze as much as possible - it is allowed, but not necessary. + * + * For raw_copy_from_user() to always points to kernel memory and no faults + * on store should happen. Interpretation of from is affected by set_fs(). + * For raw_copy_to_user() it's the other way round. + * + * Both can be inlined - it's up to architectures whether it wants to bother + * with that. They should not be used directly; they are used to implement + * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic()) + * that are used instead. Out of those, __... ones are inlined. Plain + * copy_{to,from}_user() might or might not be inlined. If you want them + * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER. + * + * NOTE: only copy_from_user() zero-pads the destination in case of short copy. + * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything + * at all; their callers absolutely must check the return value. + * + * Biarch ones should also provide raw_copy_in_user() - similar to the above, + * but both source and destination are __user pointers (affected by set_fs() + * as usual) and both source and destination can trigger faults. + */ + +static __always_inline unsigned long +__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n) +{ + kasan_check_write(to, n); + check_object_size(to, n, false); + return raw_copy_from_user(to, from, n); +} + +static __always_inline unsigned long +__copy_from_user(void *to, const void __user *from, unsigned long n) +{ + might_fault(); + kasan_check_write(to, n); + check_object_size(to, n, false); + return raw_copy_from_user(to, from, n); +} + +/** + * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking. + * @to: Destination address, in user space. + * @from: Source address, in kernel space. + * @n: Number of bytes to copy. + * + * Context: User context only. + * + * Copy data from kernel space to user space. Caller must check + * the specified block with access_ok() before calling this function. + * The caller should also make sure he pins the user space address + * so that we don't result in page fault and sleep. + */ +static __always_inline unsigned long +__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n) +{ + kasan_check_read(from, n); + check_object_size(from, n, true); + return raw_copy_to_user(to, from, n); +} + +static __always_inline unsigned long +__copy_to_user(void __user *to, const void *from, unsigned long n) +{ + might_fault(); + kasan_check_read(from, n); + check_object_size(from, n, true); + return raw_copy_to_user(to, from, n); +} + +#ifdef INLINE_COPY_FROM_USER +static inline unsigned long +_copy_from_user(void *to, const void __user *from, unsigned long n) +{ + unsigned long res = n; + if (likely(access_ok(VERIFY_READ, from, n))) + res = raw_copy_from_user(to, from, n); + if (unlikely(res)) + memset(to + (n - res), 0, res); + return res; +} +#else +extern unsigned long +_copy_from_user(void *, const void __user *, unsigned long); +#endif + +#ifdef INLINE_COPY_TO_USER +static inline unsigned long +_copy_to_user(void __user *to, const void *from, unsigned long n) +{ + if (access_ok(VERIFY_WRITE, to, n)) + n = raw_copy_to_user(to, from, n); + return n; +} +#else +extern unsigned long +_copy_to_user(void __user *, const void *, unsigned long); +#endif + +extern void __compiletime_error("usercopy buffer size is too small") +__bad_copy_user(void); + +static inline void copy_user_overflow(int size, unsigned long count) +{ + WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count); +} + +static __always_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(); + kasan_check_write(to, n); + + if (likely(sz < 0 || sz >= n)) { + check_object_size(to, n, false); + n = _copy_from_user(to, from, n); + } else if (!__builtin_constant_p(n)) + copy_user_overflow(sz, n); + else + __bad_copy_user(); + + return n; +} + +static __always_inline unsigned long __must_check +copy_to_user(void __user *to, const void *from, unsigned long n) +{ + int sz = __compiletime_object_size(from); + + kasan_check_read(from, n); + might_fault(); + + if (likely(sz < 0 || sz >= n)) { + check_object_size(from, n, true); + n = _copy_to_user(to, from, n); + } else if (!__builtin_constant_p(n)) + copy_user_overflow(sz, n); + else + __bad_copy_user(); + + return n; +} +#ifdef CONFIG_COMPAT +static __always_inline unsigned long __must_check +__copy_in_user(void __user *to, const void *from, unsigned long n) +{ + might_fault(); + return raw_copy_in_user(to, from, n); +} +static __always_inline unsigned long __must_check +copy_in_user(void __user *to, const void *from, unsigned long n) +{ + might_fault(); + if (access_ok(VERIFY_WRITE, to, n) && access_ok(VERIFY_READ, from, n)) + n = raw_copy_in_user(to, from, n); + return n; +} +#endif +#endif + static __always_inline void pagefault_disabled_inc(void) { current->pagefault_disabled++; diff --git a/lib/Makefile b/lib/Makefile index 320ac46a8725..7d875c389172 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -242,3 +242,5 @@ UBSAN_SANITIZE_ubsan.o := n obj-$(CONFIG_SBITMAP) += sbitmap.o obj-$(CONFIG_PARMAN) += parman.o + +obj-$(CONFIG_ARCH_HAS_RAW_COPY_USER) += usercopy.o diff --git a/lib/usercopy.c b/lib/usercopy.c new file mode 100644 index 000000000000..1b6010a3beb8 --- /dev/null +++ b/lib/usercopy.c @@ -0,0 +1,26 @@ +#include + +/* out-of-line parts */ + +#ifndef INLINE_COPY_FROM_USER +unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n) +{ + unsigned long res = n; + if (likely(access_ok(VERIFY_READ, from, n))) + res = raw_copy_from_user(to, from, n); + if (unlikely(res)) + memset(to + (n - res), 0, res); + return res; +} +EXPORT_SYMBOL(_copy_from_user); +#endif + +#ifndef INLINE_COPY_TO_USER +unsigned long _copy_to_user(void *to, const void __user *from, unsigned long n) +{ + if (likely(access_ok(VERIFY_WRITE, to, n))) + n = raw_copy_to_user(to, from, n); + return n; +} +EXPORT_SYMBOL(_copy_to_user); +#endif -- cgit v1.2.3-59-g8ed1b