diff options
| -rw-r--r-- | include/linux/uaccess.h | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 8aa82b1d6013..5f142c05b0dc 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -2,6 +2,7 @@ #ifndef __LINUX_UACCESS_H__ #define __LINUX_UACCESS_H__ +#include <linux/cleanup.h> #include <linux/fault-inject-usercopy.h> #include <linux/instrumented.h> #include <linux/minmax.h> @@ -35,9 +36,17 @@ #ifdef masked_user_access_begin #define can_do_masked_user_access() 1 +# ifndef masked_user_write_access_begin +# define masked_user_write_access_begin masked_user_access_begin +# endif +# ifndef masked_user_read_access_begin +# define masked_user_read_access_begin masked_user_access_begin +#endif #else #define can_do_masked_user_access() 0 #define masked_user_access_begin(src) NULL + #define masked_user_read_access_begin(src) NULL + #define masked_user_write_access_begin(src) NULL #define mask_user_address(src) (src) #endif @@ -633,6 +642,189 @@ static inline void user_access_restore(unsigned long flags) { } #define user_read_access_end user_access_end #endif +/* Define RW variant so the below _mode macro expansion works */ +#define masked_user_rw_access_begin(u) masked_user_access_begin(u) +#define user_rw_access_begin(u, s) user_access_begin(u, s) +#define user_rw_access_end() user_access_end() + +/* Scoped user access */ +#define USER_ACCESS_GUARD(_mode) \ +static __always_inline void __user * \ +class_user_##_mode##_begin(void __user *ptr) \ +{ \ + return ptr; \ +} \ + \ +static __always_inline void \ +class_user_##_mode##_end(void __user *ptr) \ +{ \ + user_##_mode##_access_end(); \ +} \ + \ +DEFINE_CLASS(user_ ##_mode## _access, void __user *, \ + class_user_##_mode##_end(_T), \ + class_user_##_mode##_begin(ptr), void __user *ptr) \ + \ +static __always_inline class_user_##_mode##_access_t \ +class_user_##_mode##_access_ptr(void __user *scope) \ +{ \ + return scope; \ +} + +USER_ACCESS_GUARD(read) +USER_ACCESS_GUARD(write) +USER_ACCESS_GUARD(rw) +#undef USER_ACCESS_GUARD + +/** + * __scoped_user_access_begin - Start a scoped user access + * @mode: The mode of the access class (read, write, rw) + * @uptr: The pointer to access user space memory + * @size: Size of the access + * @elbl: Error label to goto when the access region is rejected + * + * Internal helper for __scoped_user_access(). Don't use directly. + */ +#define __scoped_user_access_begin(mode, uptr, size, elbl) \ +({ \ + typeof(uptr) __retptr; \ + \ + if (can_do_masked_user_access()) { \ + __retptr = masked_user_##mode##_access_begin(uptr); \ + } else { \ + __retptr = uptr; \ + if (!user_##mode##_access_begin(uptr, size)) \ + goto elbl; \ + } \ + __retptr; \ +}) + +/** + * __scoped_user_access - Open a scope for user access + * @mode: The mode of the access class (read, write, rw) + * @uptr: The pointer to access user space memory + * @size: Size of the access + * @elbl: Error label to goto when the access region is rejected. It + * must be placed outside the scope + * + * If the user access function inside the scope requires a fault label, it + * can use @elbl or a different label outside the scope, which requires + * that user access which is implemented with ASM GOTO has been properly + * wrapped. See unsafe_get_user() for reference. + * + * scoped_user_rw_access(ptr, efault) { + * unsafe_get_user(rval, &ptr->rval, efault); + * unsafe_put_user(wval, &ptr->wval, efault); + * } + * return 0; + * efault: + * return -EFAULT; + * + * The scope is internally implemented as a autoterminating nested for() + * loop, which can be left with 'return', 'break' and 'goto' at any + * point. + * + * When the scope is left user_##@_mode##_access_end() is automatically + * invoked. + * + * When the architecture supports masked user access and the access region + * which is determined by @uptr and @size is not a valid user space + * address, i.e. < TASK_SIZE, the scope sets the pointer to a faulting user + * space address and does not terminate early. This optimizes for the good + * case and lets the performance uncritical bad case go through the fault. + * + * The eventual modification of the pointer is limited to the scope. + * Outside of the scope the original pointer value is unmodified, so that + * the original pointer value is available for diagnostic purposes in an + * out of scope fault path. + * + * Nesting scoped user access into a user access scope is invalid and fails + * the build. Nesting into other guards, e.g. pagefault is safe. + * + * The masked variant does not check the size of the access and relies on a + * mapping hole (e.g. guard page) to catch an out of range pointer, the + * first access to user memory inside the scope has to be within + * @uptr ... @uptr + PAGE_SIZE - 1 + * + * Don't use directly. Use scoped_masked_user_$MODE_access() instead. + */ +#define __scoped_user_access(mode, uptr, size, elbl) \ +for (bool done = false; !done; done = true) \ + for (void __user *_tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl); \ + !done; done = true) \ + for (CLASS(user_##mode##_access, scope)(_tmpptr); !done; done = true) \ + /* Force modified pointer usage within the scope */ \ + for (const typeof(uptr) uptr = _tmpptr; !done; done = true) + +/** + * scoped_user_read_access_size - Start a scoped user read access with given size + * @usrc: Pointer to the user space address to read from + * @size: Size of the access starting from @usrc + * @elbl: Error label to goto when the access region is rejected + * + * For further information see __scoped_user_access() above. + */ +#define scoped_user_read_access_size(usrc, size, elbl) \ + __scoped_user_access(read, usrc, size, elbl) + +/** + * scoped_user_read_access - Start a scoped user read access + * @usrc: Pointer to the user space address to read from + * @elbl: Error label to goto when the access region is rejected + * + * The size of the access starting from @usrc is determined via sizeof(*@usrc)). + * + * For further information see __scoped_user_access() above. + */ +#define scoped_user_read_access(usrc, elbl) \ + scoped_user_read_access_size(usrc, sizeof(*(usrc)), elbl) + +/** + * scoped_user_write_access_size - Start a scoped user write access with given size + * @udst: Pointer to the user space address to write to + * @size: Size of the access starting from @udst + * @elbl: Error label to goto when the access region is rejected + * + * For further information see __scoped_user_access() above. + */ +#define scoped_user_write_access_size(udst, size, elbl) \ + __scoped_user_access(write, udst, size, elbl) + +/** + * scoped_user_write_access - Start a scoped user write access + * @udst: Pointer to the user space address to write to + * @elbl: Error label to goto when the access region is rejected + * + * The size of the access starting from @udst is determined via sizeof(*@udst)). + * + * For further information see __scoped_user_access() above. + */ +#define scoped_user_write_access(udst, elbl) \ + scoped_user_write_access_size(udst, sizeof(*(udst)), elbl) + +/** + * scoped_user_rw_access_size - Start a scoped user read/write access with given size + * @uptr Pointer to the user space address to read from and write to + * @size: Size of the access starting from @uptr + * @elbl: Error label to goto when the access region is rejected + * + * For further information see __scoped_user_access() above. + */ +#define scoped_user_rw_access_size(uptr, size, elbl) \ + __scoped_user_access(rw, uptr, size, elbl) + +/** + * scoped_user_rw_access - Start a scoped user read/write access + * @uptr Pointer to the user space address to read from and write to + * @elbl: Error label to goto when the access region is rejected + * + * The size of the access starting from @uptr is determined via sizeof(*@uptr)). + * + * For further information see __scoped_user_access() above. + */ +#define scoped_user_rw_access(uptr, elbl) \ + scoped_user_rw_access_size(uptr, sizeof(*(uptr)), elbl) + #ifdef CONFIG_HARDENED_USERCOPY void __noreturn usercopy_abort(const char *name, const char *detail, bool to_user, unsigned long offset, |