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powerpc: Implement user_access_begin and friends

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commit 5cd623333e upstream.

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 <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/36d4fbf9e56a75994aca4ee2214c77b26a5a8d35.1579866752.git.christophe.leroy@c-s.fr
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christophe Leroy
2020-11-20 10:57:40 +11:00
committed by Greg Kroah-Hartman
parent 82973e9a1b
commit 3853ff5774
1 changed files with 46 additions and 14 deletions
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60
arch/powerpc/include/asm/uaccess.h
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@@ -106,9 +106,14 @@ struct exception_table_entry {
__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)))
@@ -162,10 +167,9 @@ 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; \
@@ -173,17 +177,26 @@ 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; \
})
@@ -249,13 +262,12 @@ 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; \
@@ -263,10 +275,16 @@ 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)
#define __get_user_nocheck(x, ptr, size) \
#define __get_user_nocheck(x, ptr, size, do_allow) \
({ \
long __gu_err; \
unsigned long __gu_val; \
@@ -275,7 +293,10 @@ 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; \
})
@@ -396,21 +417,22 @@ static inline unsigned long __copy_to_user_inatomic(void __user *to,
const void *from, unsigned long n)
{
unsigned long ret;
if (__builtin_constant_p(n) && (n <= 8)) {
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)
@@ -456,6 +478,16 @@ extern long strncpy_from_user(char *dst, const char __user *src, long count);
extern __must_check long strlen_user(const char __user *str);
extern __must_check long strnlen_user(const char __user *str, long n);
#define user_access_begin() do { } while (0)
#define user_access_end() prevent_user_access(NULL, NULL, ~0ul)
#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(__copy_to_user_inatomic(d, s, l), e)
#endif /* __ASSEMBLY__ */
#endif /* __KERNEL__ */