[PATCH v4.4 09/45] arm64: uaccess: Don't bother eliding access_ok checks in __{get, put}_user
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2019-06-14 03:12:19
Also in:
stable
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
From: Will Deacon <redacted>
commit 84624087dd7e3b482b7b11c170ebc1f329b3a218 upstream.
access_ok isn't an expensive operation once the addr_limit for the current
thread has been loaded into the cache. Given that the initial access_ok
check preceding a sequence of __{get,put}_user operations will take
the brunt of the miss, we can make the __* variants identical to the
full-fat versions, which brings with it the benefits of address masking.
The likely cost in these sequences will be from toggling PAN/UAO, which
we can address later by implementing the *_unsafe versions.
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <redacted>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ v4.4: Fixed conflicts around {__get_user|__put_user}_unaligned macros ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
arch/arm64/include/asm/uaccess.h | 62 ++++++++++++++++++--------------
1 file changed, 36 insertions(+), 26 deletions(-)
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index fc11c50af558..a34324436ce1 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h@@ -200,30 +200,35 @@ do { \ CONFIG_ARM64_PAN)); \ } while (0) -#define __get_user(x, ptr) \ +#define __get_user_check(x, ptr, err) \ ({ \ - int __gu_err = 0; \ - __get_user_err((x), (ptr), __gu_err); \ - __gu_err; \ + __typeof__(*(ptr)) __user *__p = (ptr); \ + might_fault(); \ + if (access_ok(VERIFY_READ, __p, sizeof(*__p))) { \ + __p = uaccess_mask_ptr(__p); \ + __get_user_err((x), __p, (err)); \ + } else { \ + (x) = 0; (err) = -EFAULT; \ + } \ }) #define __get_user_error(x, ptr, err) \ ({ \ - __get_user_err((x), (ptr), (err)); \ + __get_user_check((x), (ptr), (err)); \ (void)0; \ }) -#define __get_user_unaligned __get_user - -#define get_user(x, ptr) \ +#define __get_user(x, ptr) \ ({ \ - __typeof__(*(ptr)) __user *__p = (ptr); \ - might_fault(); \ - access_ok(VERIFY_READ, __p, sizeof(*__p)) ? \ - __p = uaccess_mask_ptr(__p), __get_user((x), __p) : \ - ((x) = 0, -EFAULT); \ + int __gu_err = 0; \ + __get_user_check((x), (ptr), __gu_err); \ + __gu_err; \ }) +#define __get_user_unaligned __get_user + +#define get_user __get_user + #define __put_user_asm(instr, reg, x, addr, err) \ asm volatile( \ "1: " instr " " reg "1, [%2]\n" \
@@ -266,30 +271,35 @@ do { \ CONFIG_ARM64_PAN)); \ } while (0) -#define __put_user(x, ptr) \ +#define __put_user_check(x, ptr, err) \ ({ \ - int __pu_err = 0; \ - __put_user_err((x), (ptr), __pu_err); \ - __pu_err; \ + __typeof__(*(ptr)) __user *__p = (ptr); \ + might_fault(); \ + if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) { \ + __p = uaccess_mask_ptr(__p); \ + __put_user_err((x), __p, (err)); \ + } else { \ + (err) = -EFAULT; \ + } \ }) #define __put_user_error(x, ptr, err) \ ({ \ - __put_user_err((x), (ptr), (err)); \ + __put_user_check((x), (ptr), (err)); \ (void)0; \ }) -#define __put_user_unaligned __put_user - -#define put_user(x, ptr) \ +#define __put_user(x, ptr) \ ({ \ - __typeof__(*(ptr)) __user *__p = (ptr); \ - might_fault(); \ - access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ? \ - __p = uaccess_mask_ptr(__p), __put_user((x), __p) : \ - -EFAULT; \ + int __pu_err = 0; \ + __put_user_check((x), (ptr), __pu_err); \ + __pu_err; \ }) +#define __put_user_unaligned __put_user + +#define put_user __put_user + extern unsigned long __must_check __copy_from_user(void *to, const void __user *from, unsigned long n); extern unsigned long __must_check __copy_to_user(void __user *to, const void *from, unsigned long n); extern unsigned long __must_check __copy_in_user(void __user *to, const void __user *from, unsigned long n);
--
2.21.0.rc0.269.g1a574e7a288b
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