[PATCH RFC v2 23/25] kmsan: hooks for copy_to_user() and friends

[glider@google.com]

Memory that is copied from userspace must be unpoisoned.
Before copying memory to userspace, check it and report an error if it
contains uninitialized bits.

Signed-off-by: Alexander Potapenko <glider@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: linux-mm@kvack.org
---

Change-Id: I38428b9c7d1909b8441dcec1749b080494a7af99
---
 arch/x86/include/asm/uaccess.h   | 12 ++++++++++++
 include/asm-generic/cacheflush.h |  7 ++++++-
 include/asm-generic/uaccess.h    | 12 ++++++++++--
 include/linux/uaccess.h          | 32 +++++++++++++++++++++++++++-----
 lib/iov_iter.c                   |  6 ++++++
 lib/usercopy.c                   |  6 +++++-
 6 files changed, 66 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 61d93f062a36..ac4b26583f7c 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -6,6 +6,7 @@
  */
 #include <linux/compiler.h>
 #include <linux/kasan-checks.h>
+#include <linux/kmsan-checks.h>
 #include <linux/string.h>
 #include <asm/asm.h>
 #include <asm/page.h>
@@ -174,6 +175,7 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
 			ASM_CALL_CONSTRAINT				\
 		     : "0" (ptr), "i" (sizeof(*(ptr))));		\
 	(x) = (__force __typeof__(*(ptr))) __val_gu;			\
+	kmsan_unpoison_shadow(&(x), sizeof(*(ptr)));			\
 	__builtin_expect(__ret_gu, 0);					\
 })
 
@@ -248,6 +250,7 @@ extern void __put_user_8(void);
 	__chk_user_ptr(ptr);					\
 	might_fault();						\
 	__pu_val = x;						\
+	kmsan_check_memory(&(__pu_val), sizeof(*(ptr)));	\
 	switch (sizeof(*(ptr))) {				\
 	case 1:							\
 		__put_user_x(1, __pu_val, ptr, __ret_pu);	\
@@ -270,7 +273,9 @@ extern void __put_user_8(void);
 
 #define __put_user_size(x, ptr, size, label)				\
 do {									\
+	__typeof__(*(ptr)) __pus_val = x;				\
 	__chk_user_ptr(ptr);						\
+	kmsan_check_memory(&(__pus_val), size);				\
 	switch (size) {							\
 	case 1:								\
 		__put_user_goto(x, ptr, "b", "b", "iq", label);	\
@@ -295,7 +300,10 @@ do {									\
  */
 #define __put_user_size_ex(x, ptr, size)				\
 do {									\
+	__typeof__(*(ptr)) __puse_val;					\
 	__chk_user_ptr(ptr);						\
+	__puse_val = x;							\
+	kmsan_check_memory(&(__puse_val), size);			\
 	switch (size) {							\
 	case 1:								\
 		__put_user_asm_ex(x, ptr, "b", "b", "iq");		\
@@ -363,6 +371,7 @@ do {									\
 	default:							\
 		(x) = __get_user_bad();					\
 	}								\
+	kmsan_unpoison_shadow(&(x), size);				\
 } while (0)
 
 #define __get_user_asm(x, addr, err, itype, rtype, ltype, errret)	\
@@ -413,6 +422,7 @@ do {									\
 	default:							\
 		(x) = __get_user_bad();					\
 	}								\
+	kmsan_unpoison_shadow(&(x), size);				\
 } while (0)
 
 #define __get_user_asm_ex(x, addr, itype, rtype, ltype)			\
@@ -428,11 +438,13 @@ do {									\
 #define __put_user_nocheck(x, ptr, size)			\
 ({								\
 	__label__ __pu_label;					\
+	__typeof__(*(ptr)) __pun_val = x;			\
 	int __pu_err = -EFAULT;					\
 	__typeof__(*(ptr)) __pu_val = (x);			\
 	__typeof__(ptr) __pu_ptr = (ptr);			\
 	__typeof__(size) __pu_size = (size);			\
 	__uaccess_begin();					\
+	kmsan_check_memory(&(__pun_val), size);			\
 	__put_user_size(__pu_val, __pu_ptr, __pu_size, __pu_label);	\
 	__pu_err = 0;						\
 __pu_label:							\
diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cacheflush.h
index a950a22c4890..707531dccf5e 100644
--- a/include/asm-generic/cacheflush.h
+++ b/include/asm-generic/cacheflush.h
@@ -4,6 +4,7 @@
 
 /* Keep includes the same across arches.  */
 #include <linux/mm.h>
+#include <linux/kmsan-checks.h>
 
 #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0
 
@@ -72,10 +73,14 @@ static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
 
 #define copy_to_user_page(vma, page, vaddr, dst, src, len) \
 	do { \
+		kmsan_check_memory(src, len); \
 		memcpy(dst, src, len); \
 		flush_icache_user_range(vma, page, vaddr, len); \
 	} while (0)
 #define copy_from_user_page(vma, page, vaddr, dst, src, len) \
-	memcpy(dst, src, len)
+	do { \
+		memcpy(dst, src, len); \
+		kmsan_unpoison_shadow(dst, len); \
+	} while (0)
 
 #endif /* __ASM_CACHEFLUSH_H */
diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index e935318804f8..18a50333ffc0 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -142,7 +142,11 @@ static inline int __access_ok(unsigned long addr, unsigned long size)
 
 static inline int __put_user_fn(size_t size, void __user *ptr, void *x)
 {
-	return unlikely(raw_copy_to_user(ptr, x, size)) ? -EFAULT : 0;
+	int n;
+
+	n = raw_copy_to_user(ptr, x, size);
+	kmsan_copy_to_user(ptr, x, size, n);
+	return unlikely(n) ? -EFAULT : 0;
 }
 
 #define __put_user_fn(sz, u, k)	__put_user_fn(sz, u, k)
@@ -203,7 +207,11 @@ extern int __put_user_bad(void) __attribute__((noreturn));
 #ifndef __get_user_fn
 static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)
 {
-	return unlikely(raw_copy_from_user(x, ptr, size)) ? -EFAULT : 0;
+	int copied, to_copy = size;
+
+	copied = raw_copy_from_user(x, ptr, size);
+	kmsan_unpoison_shadow(to, to_copy - res);
+	return unlikely(copied) ? -EFAULT : 0;
 }
 
 #define __get_user_fn(sz, u, k)	__get_user_fn(sz, u, k)
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index d4ee6e942562..4257b5f80689 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -5,6 +5,7 @@
 #include <linux/sched.h>
 #include <linux/thread_info.h>
 #include <linux/kasan-checks.h>
+#include <linux/kmsan-checks.h>
 
 #define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
 
@@ -58,18 +59,26 @@
 static __always_inline __must_check unsigned long
 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
 {
+	unsigned long to_copy = n;
+
 	kasan_check_write(to, n);
 	check_object_size(to, n, false);
-	return raw_copy_from_user(to, from, n);
+	n = raw_copy_from_user(to, from, n);
+	kmsan_unpoison_shadow(to, to_copy - n);
+	return n;
 }
 
 static __always_inline __must_check unsigned long
 __copy_from_user(void *to, const void __user *from, unsigned long n)
 {
+	unsigned long to_copy = n;
+
 	might_fault();
 	kasan_check_write(to, n);
 	check_object_size(to, n, false);
-	return raw_copy_from_user(to, from, n);
+	n = raw_copy_from_user(to, from, n);
+	kmsan_unpoison_shadow(to, to_copy - n);
+	return n;
 }
 
 /**
@@ -88,29 +97,39 @@ __copy_from_user(void *to, const void __user *from, unsigned long n)
 static __always_inline __must_check unsigned long
 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
 {
+	unsigned long to_copy = n;
+
 	kasan_check_read(from, n);
 	check_object_size(from, n, true);
-	return raw_copy_to_user(to, from, n);
+	n = raw_copy_to_user(to, from, n);
+	kmsan_copy_to_user(to, from, to_copy, n);
+	return n;
 }
 
 static __always_inline __must_check unsigned long
 __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+	unsigned long to_copy = n;
+
 	might_fault();
 	kasan_check_read(from, n);
 	check_object_size(from, n, true);
-	return raw_copy_to_user(to, from, n);
+	n = raw_copy_to_user(to, from, n);
+	kmsan_copy_to_user(to, from, to_copy, n);
+	return n;
 }
 
 #ifdef INLINE_COPY_FROM_USER
 static inline __must_check unsigned long
 _copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	unsigned long res = n;
+	unsigned long res = n, to_copy = n;
+
 	might_fault();
 	if (likely(access_ok(from, n))) {
 		kasan_check_write(to, n);
 		res = raw_copy_from_user(to, from, n);
+		kmsan_unpoison_shadow(to, to_copy - res);
 	}
 	if (unlikely(res))
 		memset(to + (n - res), 0, res);
@@ -125,10 +144,13 @@ _copy_from_user(void *, const void __user *, unsigned long);
 static inline __must_check unsigned long
 _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+	unsigned long to_copy = n;
+
 	might_fault();
 	if (access_ok(to, n)) {
 		kasan_check_read(from, n);
 		n = raw_copy_to_user(to, from, n);
+		kmsan_copy_to_user(to, from, to_copy, n);
 	}
 	return n;
 }
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 639d5e7014c1..f038676068b2 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -137,18 +137,24 @@
 
 static int copyout(void __user *to, const void *from, size_t n)
 {
+	size_t to_copy = n;
+
 	if (access_ok(to, n)) {
 		kasan_check_read(from, n);
 		n = raw_copy_to_user(to, from, n);
+		kmsan_copy_to_user(to, from, to_copy, n);
 	}
 	return n;
 }
 
 static int copyin(void *to, const void __user *from, size_t n)
 {
+	size_t to_copy = n;
+
 	if (access_ok(from, n)) {
 		kasan_check_write(to, n);
 		n = raw_copy_from_user(to, from, n);
+		kmsan_unpoison_shadow(to, to_copy - n);
 	}
 	return n;
 }
diff --git a/lib/usercopy.c b/lib/usercopy.c
index cbb4d9ec00f2..abfd93edecba 100644
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <linux/kmsan-checks.h>
 #include <linux/uaccess.h>
 #include <linux/bitops.h>
 
@@ -7,11 +8,12 @@
 #ifndef INLINE_COPY_FROM_USER
 unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	unsigned long res = n;
+	unsigned long res = n, to_copy = n;
 	might_fault();
 	if (likely(access_ok(from, n))) {
 		kasan_check_write(to, n);
 		res = raw_copy_from_user(to, from, n);
+		kmsan_unpoison_shadow(to, to_copy - res);
 	}
 	if (unlikely(res))
 		memset(to + (n - res), 0, res);
@@ -23,10 +25,12 @@ EXPORT_SYMBOL(_copy_from_user);
 #ifndef INLINE_COPY_TO_USER
 unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+	unsigned long to_copy = n;
 	might_fault();
 	if (likely(access_ok(to, n))) {
 		kasan_check_read(from, n);
 		n = raw_copy_to_user(to, from, n);
+		kmsan_copy_to_user(to, from, to_copy, n);
 	}
 	return n;
 }
-- 
2.24.0.rc0.303.g954a862665-goog