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powerpc/uaccess: Implement user_read_access_begin and user_write_access_begin

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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 <christophe.leroy@c-s.fr>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6c83af0f0809ef2a955c39ac622767f6cbede035.1585898438.git.christophe.leroy@c-s.fr
This commit is contained in:
Christophe Leroy 2020-04-03 07:20:53 +00:00 committed by Michael Ellerman
parent 1f59cc3482
commit 4fe5cda9f8
3 changed files with 37 additions and 3 deletions
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4
arch/powerpc/include/asm/book3s/32/kup.h
View file

@ -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))

14
arch/powerpc/include/asm/kup.h
View file

@ -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 <asm/book3s/64/kup-radix.h>
@ -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_ */

22
arch/powerpc/include/asm/uaccess.h
View file

@ -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)