From 5cd623333e7cf4e3a334c70529268b65f2a6c2c7 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Fri, 24 Jan 2020 11:54:44 +0000 Subject: [PATCH] powerpc: Implement user_access_begin and friends Today, when a function like strncpy_from_user() is called, the userspace access protection is de-activated and re-activated for every word read. By implementing user_access_begin and friends, the protection is de-activated at the beginning of the copy and re-activated at the end. Implement user_access_begin(), user_access_end() and unsafe_get_user(), unsafe_put_user() and unsafe_copy_to_user() For the time being, we keep user_access_save() and user_access_restore() as nops. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/36d4fbf9e56a75994aca4ee2214c77b26a5a8d35.1579866752.git.christophe.leroy@c-s.fr --- arch/powerpc/include/asm/uaccess.h | 85 +++++++++++++++++++++++++++++--------- 1 file changed, 66 insertions(+), 19 deletions(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index cafad1960e76..af905d7fc1df 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -91,9 +91,14 @@ static inline int __access_ok(unsigned long addr, unsigned long size, __put_user_check((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr))) #define __get_user(x, ptr) \ - __get_user_nocheck((x), (ptr), sizeof(*(ptr))) + __get_user_nocheck((x), (ptr), sizeof(*(ptr)), true) #define __put_user(x, ptr) \ - __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr))) + __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), true) + +#define __get_user_allowed(x, ptr) \ + __get_user_nocheck((x), (ptr), sizeof(*(ptr)), false) +#define __put_user_allowed(x, ptr) \ + __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), false) #define __get_user_inatomic(x, ptr) \ __get_user_nosleep((x), (ptr), sizeof(*(ptr))) @@ -138,10 +143,9 @@ extern long __put_user_bad(void); : "r" (x), "b" (addr), "i" (-EFAULT), "0" (err)) #endif /* __powerpc64__ */ -#define __put_user_size(x, ptr, size, retval) \ +#define __put_user_size_allowed(x, ptr, size, retval) \ do { \ retval = 0; \ - allow_write_to_user(ptr, size); \ switch (size) { \ case 1: __put_user_asm(x, ptr, retval, "stb"); break; \ case 2: __put_user_asm(x, ptr, retval, "sth"); break; \ @@ -149,17 +153,26 @@ do { \ case 8: __put_user_asm2(x, ptr, retval); break; \ default: __put_user_bad(); \ } \ +} while (0) + +#define __put_user_size(x, ptr, size, retval) \ +do { \ + allow_write_to_user(ptr, size); \ + __put_user_size_allowed(x, ptr, size, retval); \ prevent_write_to_user(ptr, size); \ } while (0) -#define __put_user_nocheck(x, ptr, size) \ +#define __put_user_nocheck(x, ptr, size, do_allow) \ ({ \ long __pu_err; \ __typeof__(*(ptr)) __user *__pu_addr = (ptr); \ if (!is_kernel_addr((unsigned long)__pu_addr)) \ might_fault(); \ __chk_user_ptr(ptr); \ - __put_user_size((x), __pu_addr, (size), __pu_err); \ + if (do_allow) \ + __put_user_size((x), __pu_addr, (size), __pu_err); \ + else \ + __put_user_size_allowed((x), __pu_addr, (size), __pu_err); \ __pu_err; \ }) @@ -236,13 +249,12 @@ extern long __get_user_bad(void); : "b" (addr), "i" (-EFAULT), "0" (err)) #endif /* __powerpc64__ */ -#define __get_user_size(x, ptr, size, retval) \ +#define __get_user_size_allowed(x, ptr, size, retval) \ do { \ retval = 0; \ __chk_user_ptr(ptr); \ if (size > sizeof(x)) \ (x) = __get_user_bad(); \ - allow_read_from_user(ptr, size); \ switch (size) { \ case 1: __get_user_asm(x, ptr, retval, "lbz"); break; \ case 2: __get_user_asm(x, ptr, retval, "lhz"); break; \ @@ -250,6 +262,12 @@ do { \ case 8: __get_user_asm2(x, ptr, retval); break; \ default: (x) = __get_user_bad(); \ } \ +} while (0) + +#define __get_user_size(x, ptr, size, retval) \ +do { \ + allow_read_from_user(ptr, size); \ + __get_user_size_allowed(x, ptr, size, retval); \ prevent_read_from_user(ptr, size); \ } while (0) @@ -260,7 +278,7 @@ do { \ #define __long_type(x) \ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL)) -#define __get_user_nocheck(x, ptr, size) \ +#define __get_user_nocheck(x, ptr, size, do_allow) \ ({ \ long __gu_err; \ __long_type(*(ptr)) __gu_val; \ @@ -269,7 +287,10 @@ do { \ if (!is_kernel_addr((unsigned long)__gu_addr)) \ might_fault(); \ barrier_nospec(); \ - __get_user_size(__gu_val, __gu_addr, (size), __gu_err); \ + if (do_allow) \ + __get_user_size(__gu_val, __gu_addr, (size), __gu_err); \ + else \ + __get_user_size_allowed(__gu_val, __gu_addr, (size), __gu_err); \ (x) = (__typeof__(*(ptr)))__gu_val; \ __gu_err; \ }) @@ -356,33 +377,40 @@ static inline unsigned long raw_copy_from_user(void *to, return ret; } -static inline unsigned long raw_copy_to_user(void __user *to, - const void *from, unsigned long n) +static inline unsigned long +raw_copy_to_user_allowed(void __user *to, const void *from, unsigned long n) { - unsigned long ret; if (__builtin_constant_p(n) && (n <= 8)) { - ret = 1; + unsigned long ret = 1; switch (n) { case 1: - __put_user_size(*(u8 *)from, (u8 __user *)to, 1, ret); + __put_user_size_allowed(*(u8 *)from, (u8 __user *)to, 1, ret); break; case 2: - __put_user_size(*(u16 *)from, (u16 __user *)to, 2, ret); + __put_user_size_allowed(*(u16 *)from, (u16 __user *)to, 2, ret); break; case 4: - __put_user_size(*(u32 *)from, (u32 __user *)to, 4, ret); + __put_user_size_allowed(*(u32 *)from, (u32 __user *)to, 4, ret); break; case 8: - __put_user_size(*(u64 *)from, (u64 __user *)to, 8, ret); + __put_user_size_allowed(*(u64 *)from, (u64 __user *)to, 8, ret); break; } if (ret == 0) return 0; } + return __copy_tofrom_user(to, (__force const void __user *)from, n); +} + +static inline unsigned long +raw_copy_to_user(void __user *to, const void *from, unsigned long n) +{ + unsigned long ret; + allow_write_to_user(to, n); - ret = __copy_tofrom_user(to, (__force const void __user *)from, n); + ret = raw_copy_to_user_allowed(to, from, n); prevent_write_to_user(to, n); return ret; } @@ -428,4 +456,23 @@ extern long __copy_from_user_flushcache(void *dst, const void __user *src, extern void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len); +static __must_check inline bool user_access_begin(const void __user *ptr, size_t len) +{ + if (unlikely(!access_ok(ptr, len))) + return false; + allow_read_write_user((void __user *)ptr, ptr, len); + return true; +} +#define user_access_begin user_access_begin +#define user_access_end prevent_current_access_user + +static inline unsigned long user_access_save(void) { return 0UL; } +static inline void user_access_restore(unsigned long flags) { } + +#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0) +#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e) +#define unsafe_put_user(x, p, e) unsafe_op_wrap(__put_user_allowed(x, p), e) +#define unsafe_copy_to_user(d, s, l, e) \ + unsafe_op_wrap(raw_copy_to_user_allowed(d, s, l), e) + #endif /* _ARCH_POWERPC_UACCESS_H */ -- 2.11.0