From 4fe5cda9f89d0aea8e915b7c96ae34bda4e12e51 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Fri, 3 Apr 2020 07:20:53 +0000 Subject: [PATCH] powerpc/uaccess: Implement user_read_access_begin and user_write_access_begin Add support for selective read or write user access with user_read_access_begin/end and user_write_access_begin/end. Signed-off-by: Christophe Leroy Reviewed-by: Kees Cook Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/6c83af0f0809ef2a955c39ac622767f6cbede035.1585898438.git.christophe.leroy@c-s.fr --- arch/powerpc/include/asm/book3s/32/kup.h | 4 ++-- arch/powerpc/include/asm/kup.h | 14 +++++++++++++- arch/powerpc/include/asm/uaccess.h | 22 ++++++++++++++++++++++ 3 files changed, 37 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h index 3c0ba22..1617e73 100644 --- a/arch/powerpc/include/asm/book3s/32/kup.h +++ b/arch/powerpc/include/asm/book3s/32/kup.h @@ -108,7 +108,7 @@ static __always_inline void allow_user_access(void __user *to, const void __user u32 addr, end; BUILD_BUG_ON(!__builtin_constant_p(dir)); - BUILD_BUG_ON(dir == KUAP_CURRENT); + BUILD_BUG_ON(dir & ~KUAP_READ_WRITE); if (!(dir & KUAP_WRITE)) return; @@ -131,7 +131,7 @@ static __always_inline void prevent_user_access(void __user *to, const void __us BUILD_BUG_ON(!__builtin_constant_p(dir)); - if (dir == KUAP_CURRENT) { + if (dir & KUAP_CURRENT_WRITE) { u32 kuap = current->thread.kuap; if (unlikely(!kuap)) diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h index 92bcd1a..c745ee4 100644 --- a/arch/powerpc/include/asm/kup.h +++ b/arch/powerpc/include/asm/kup.h @@ -10,7 +10,9 @@ * Use the current saved situation instead of the to/from/size params. * Used on book3s/32 */ -#define KUAP_CURRENT 4 +#define KUAP_CURRENT_READ 4 +#define KUAP_CURRENT_WRITE 8 +#define KUAP_CURRENT (KUAP_CURRENT_READ | KUAP_CURRENT_WRITE) #ifdef CONFIG_PPC64 #include @@ -101,6 +103,16 @@ static inline void prevent_current_access_user(void) prevent_user_access(NULL, NULL, ~0UL, KUAP_CURRENT); } +static inline void prevent_current_read_from_user(void) +{ + prevent_user_access(NULL, NULL, ~0UL, KUAP_CURRENT_READ); +} + +static inline void prevent_current_write_to_user(void) +{ + prevent_user_access(NULL, NULL, ~0UL, KUAP_CURRENT_WRITE); +} + #endif /* !__ASSEMBLY__ */ #endif /* _ASM_POWERPC_KUAP_H_ */ diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 42b6c44..62cc8d7 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -532,6 +532,28 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t #define user_access_save prevent_user_access_return #define user_access_restore restore_user_access +static __must_check inline bool +user_read_access_begin(const void __user *ptr, size_t len) +{ + if (unlikely(!access_ok(ptr, len))) + return false; + allow_read_from_user(ptr, len); + return true; +} +#define user_read_access_begin user_read_access_begin +#define user_read_access_end prevent_current_read_from_user + +static __must_check inline bool +user_write_access_begin(const void __user *ptr, size_t len) +{ + if (unlikely(!access_ok(ptr, len))) + return false; + allow_write_to_user((void __user *)ptr, len); + return true; +} +#define user_write_access_begin user_write_access_begin +#define user_write_access_end prevent_current_write_to_user + #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) __put_user_goto(x, p, e) -- 2.7.4