Merge tag 'usercopy-v4.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kees...

Pull hardened usercopy fixes from Kees Cook:

 - inline copy_*_user() for correct use of __builtin_const_p() for
   hardened usercopy and the recent compile-time checks.

 - switch hardened usercopy to only check non-const size arguments to
   avoid meaningless checks on likely-sane const values.

 - update lkdtm usercopy tests to compenstate for the const checking.

* tag 'usercopy-v4.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  lkdtm: adjust usercopy tests to bypass const checks
  usercopy: fold builtin_const check into inline function
  x86/uaccess: force copy_*_user() to be inlined

diff --git a/arch/ia64/include/asm/uaccess.h b/arch/ia64/include/asm/uaccess.h
index 465c709..0472927 100644 (file)
--- a/arch/ia64/include/asm/uaccess.h
+++ b/arch/ia64/include/asm/uaccess.h
@@ -241,8 +241,7 @@ extern unsigned long __must_check __copy_user (void __user *to, const void __use
 static inline unsigned long
 __copy_to_user (void __user *to, const void *from, unsigned long count)
 {
-       if (!__builtin_constant_p(count))
-               check_object_size(from, count, true);
+       check_object_size(from, count, true);
 
        return __copy_user(to, (__force void __user *) from, count);
 }
@@ -250,8 +249,7 @@ __copy_to_user (void __user *to, const void *from, unsigned long count)
 static inline unsigned long
 __copy_from_user (void *to, const void __user *from, unsigned long count)
 {
-       if (!__builtin_constant_p(count))
-               check_object_size(to, count, false);
+       check_object_size(to, count, false);
 
        return __copy_user((__force void __user *) to, from, count);
 }
@@ -265,8 +263,7 @@ __copy_from_user (void *to, const void __user *from, unsigned long count)
        long __cu_len = (n);                                                            \
                                                                                        \
        if (__access_ok(__cu_to, __cu_len, get_fs())) {                                 \
-               if (!__builtin_constant_p(n))                                           \
-                       check_object_size(__cu_from, __cu_len, true);                   \
+               check_object_size(__cu_from, __cu_len, true);                   \
                __cu_len = __copy_user(__cu_to, (__force void __user *)  __cu_from, __cu_len);  \
        }                                                                               \
        __cu_len;                                                                       \
@@ -280,8 +277,7 @@ __copy_from_user (void *to, const void __user *from, unsigned long count)
                                                                                        \
        __chk_user_ptr(__cu_from);                                                      \
        if (__access_ok(__cu_from, __cu_len, get_fs())) {                               \
-               if (!__builtin_constant_p(n))                                           \
-                       check_object_size(__cu_to, __cu_len, false);                    \
+               check_object_size(__cu_to, __cu_len, false);                    \
                __cu_len = __copy_user((__force void __user *) __cu_to, __cu_from, __cu_len);   \
        }                                                                               \
        __cu_len;                                                                       \

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index c1dc6c1..f1e3824 100644 (file)
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -311,14 +311,12 @@ static inline unsigned long copy_from_user(void *to,
        unsigned long over;
 
        if (access_ok(VERIFY_READ, from, n)) {
-               if (!__builtin_constant_p(n))
-                       check_object_size(to, n, false);
+               check_object_size(to, n, false);
                return __copy_tofrom_user((__force void __user *)to, from, n);
        }
        if ((unsigned long)from < TASK_SIZE) {
                over = (unsigned long)from + n - TASK_SIZE;
-               if (!__builtin_constant_p(n - over))
-                       check_object_size(to, n - over, false);
+               check_object_size(to, n - over, false);
                return __copy_tofrom_user((__force void __user *)to, from,
                                n - over) + over;
        }
@@ -331,14 +329,12 @@ static inline unsigned long copy_to_user(void __user *to,
        unsigned long over;
 
        if (access_ok(VERIFY_WRITE, to, n)) {
-               if (!__builtin_constant_p(n))
-                       check_object_size(from, n, true);
+               check_object_size(from, n, true);
                return __copy_tofrom_user(to, (__force void __user *)from, n);
        }
        if ((unsigned long)to < TASK_SIZE) {
                over = (unsigned long)to + n - TASK_SIZE;
-               if (!__builtin_constant_p(n))
-                       check_object_size(from, n - over, true);
+               check_object_size(from, n - over, true);
                return __copy_tofrom_user(to, (__force void __user *)from,
                                n - over) + over;
        }
@@ -383,8 +379,7 @@ static inline unsigned long __copy_from_user_inatomic(void *to,
                        return 0;
        }
 
-       if (!__builtin_constant_p(n))
-               check_object_size(to, n, false);
+       check_object_size(to, n, false);
 
        return __copy_tofrom_user((__force void __user *)to, from, n);
 }
@@ -412,8 +407,8 @@ static inline unsigned long __copy_to_user_inatomic(void __user *to,
                if (ret == 0)
                        return 0;
        }
-       if (!__builtin_constant_p(n))
-               check_object_size(from, n, true);
+
+       check_object_size(from, n, true);
 
        return __copy_tofrom_user(to, (__force const void __user *)from, n);
 }

diff --git a/arch/sparc/include/asm/uaccess_32.h b/arch/sparc/include/asm/uaccess_32.h
index 341a5a1..e722c51 100644 (file)
--- a/arch/sparc/include/asm/uaccess_32.h
+++ b/arch/sparc/include/asm/uaccess_32.h
@@ -249,8 +249,7 @@ unsigned long __copy_user(void __user *to, const void __user *from, unsigned lon
 static inline unsigned long copy_to_user(void __user *to, const void *from, unsigned long n)
 {
        if (n && __access_ok((unsigned long) to, n)) {
-               if (!__builtin_constant_p(n))
-                       check_object_size(from, n, true);
+               check_object_size(from, n, true);
                return __copy_user(to, (__force void __user *) from, n);
        } else
                return n;
@@ -258,16 +257,14 @@ static inline unsigned long copy_to_user(void __user *to, const void *from, unsi
 
 static inline unsigned long __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-       if (!__builtin_constant_p(n))
-               check_object_size(from, n, true);
+       check_object_size(from, n, true);
        return __copy_user(to, (__force void __user *) from, n);
 }
 
 static inline unsigned long copy_from_user(void *to, const void __user *from, unsigned long n)
 {
        if (n && __access_ok((unsigned long) from, n)) {
-               if (!__builtin_constant_p(n))
-                       check_object_size(to, n, false);
+               check_object_size(to, n, false);
                return __copy_user((__force void __user *) to, from, n);
        } else
                return n;

diff --git a/arch/sparc/include/asm/uaccess_64.h b/arch/sparc/include/asm/uaccess_64.h
index 8bda94f..37a315d 100644 (file)
--- a/arch/sparc/include/asm/uaccess_64.h
+++ b/arch/sparc/include/asm/uaccess_64.h
@@ -212,8 +212,7 @@ copy_from_user(void *to, const void __user *from, unsigned long size)
 {
        unsigned long ret;
 
-       if (!__builtin_constant_p(size))
-               check_object_size(to, size, false);
+       check_object_size(to, size, false);
 
        ret = ___copy_from_user(to, from, size);
        if (unlikely(ret))
@@ -233,8 +232,8 @@ copy_to_user(void __user *to, const void *from, unsigned long size)
 {
        unsigned long ret;
 
-       if (!__builtin_constant_p(size))
-               check_object_size(from, size, true);
+       check_object_size(from, size, true);
+
        ret = ___copy_to_user(to, from, size);
        if (unlikely(ret))
                ret = copy_to_user_fixup(to, from, size);

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index c3f2911..e3af86f 100644 (file)
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -705,7 +705,7 @@ static inline void copy_user_overflow(int size, unsigned long count)
        WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
 }
 
-static inline unsigned long __must_check
+static __always_inline unsigned long __must_check
 copy_from_user(void *to, const void __user *from, unsigned long n)
 {
        int sz = __compiletime_object_size(to);
@@ -725,7 +725,7 @@ copy_from_user(void *to, const void __user *from, unsigned long n)
        return n;
 }
 
-static inline unsigned long __must_check
+static __always_inline unsigned long __must_check
 copy_to_user(void __user *to, const void *from, unsigned long n)
 {
        int sz = __compiletime_object_size(from);

diff --git a/drivers/misc/lkdtm_usercopy.c b/drivers/misc/lkdtm_usercopy.c
index 5525a20..1dd6114 100644 (file)
--- a/drivers/misc/lkdtm_usercopy.c
+++ b/drivers/misc/lkdtm_usercopy.c
@@ -9,7 +9,15 @@
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
 
-static size_t cache_size = 1024;
+/*
+ * Many of the tests here end up using const sizes, but those would
+ * normally be ignored by hardened usercopy, so force the compiler
+ * into choosing the non-const path to make sure we trigger the
+ * hardened usercopy checks by added "unconst" to all the const copies,
+ * and making sure "cache_size" isn't optimized into a const.
+ */
+static volatile size_t unconst = 0;
+static volatile size_t cache_size = 1024;
 static struct kmem_cache *bad_cache;
 
 static const unsigned char test_text[] = "This is a test.\n";
@@ -67,14 +75,14 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
        if (to_user) {
                pr_info("attempting good copy_to_user of local stack\n");
                if (copy_to_user((void __user *)user_addr, good_stack,
-                                sizeof(good_stack))) {
+                                unconst + sizeof(good_stack))) {
                        pr_warn("copy_to_user failed unexpectedly?!\n");
                        goto free_user;
                }
 
                pr_info("attempting bad copy_to_user of distant stack\n");
                if (copy_to_user((void __user *)user_addr, bad_stack,
-                                sizeof(good_stack))) {
+                                unconst + sizeof(good_stack))) {
                        pr_warn("copy_to_user failed, but lacked Oops\n");
                        goto free_user;
                }
@@ -88,14 +96,14 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
 
                pr_info("attempting good copy_from_user of local stack\n");
                if (copy_from_user(good_stack, (void __user *)user_addr,
-                                  sizeof(good_stack))) {
+                                  unconst + sizeof(good_stack))) {
                        pr_warn("copy_from_user failed unexpectedly?!\n");
                        goto free_user;
                }
 
                pr_info("attempting bad copy_from_user of distant stack\n");
                if (copy_from_user(bad_stack, (void __user *)user_addr,
-                                  sizeof(good_stack))) {
+                                  unconst + sizeof(good_stack))) {
                        pr_warn("copy_from_user failed, but lacked Oops\n");
                        goto free_user;
                }
@@ -109,7 +117,7 @@ static void do_usercopy_heap_size(bool to_user)
 {
        unsigned long user_addr;
        unsigned char *one, *two;
-       const size_t size = 1024;
+       size_t size = unconst + 1024;
 
        one = kmalloc(size, GFP_KERNEL);
        two = kmalloc(size, GFP_KERNEL);
@@ -285,13 +293,14 @@ void lkdtm_USERCOPY_KERNEL(void)
 
        pr_info("attempting good copy_to_user from kernel rodata\n");
        if (copy_to_user((void __user *)user_addr, test_text,
-                        sizeof(test_text))) {
+                        unconst + sizeof(test_text))) {
                pr_warn("copy_to_user failed unexpectedly?!\n");
                goto free_user;
        }
 
        pr_info("attempting bad copy_to_user from kernel text\n");
-       if (copy_to_user((void __user *)user_addr, vm_mmap, PAGE_SIZE)) {
+       if (copy_to_user((void __user *)user_addr, vm_mmap,
+                        unconst + PAGE_SIZE)) {
                pr_warn("copy_to_user failed, but lacked Oops\n");
                goto free_user;
        }

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index cbd8990..10c9e60 100644 (file)
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -121,7 +121,8 @@ extern void __check_object_size(const void *ptr, unsigned long n,
 static inline void check_object_size(const void *ptr, unsigned long n,
                                     bool to_user)
 {
-       __check_object_size(ptr, n, to_user);
+       if (!__builtin_constant_p(n))
+               __check_object_size(ptr, n, to_user);
 }
 #else
 static inline void check_object_size(const void *ptr, unsigned long n,