ARM: fix uaccess_with_memcpy() with SW_DOMAIN_PAN

The uaccess_with_memcpy() code is currently incompatible with the SW
PAN code: it takes locks within the region that we've changed the DACR,
potentially sleeping as a result.  As we do not save and restore the
DACR across co-operative sleep events, can lead to an incorrect DACR
value later in this code path.

Reported-by: Peter Rosin <peda@axentia.se>
Tested-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 27 insertions, 6 deletions

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 8cc85a4ebec2..35c9db857ebe 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -510,10 +510,14 @@ __copy_to_user_std(void __user *to, const void *from, unsigned long n);
 static inline unsigned long __must_check
 __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+#ifndef CONFIG_UACCESS_WITH_MEMCPY
         unsigned int __ua_flags = uaccess_save_and_enable();
         n = arm_copy_to_user(to, from, n);
         uaccess_restore(__ua_flags);
         return n;
+#else
+        return arm_copy_to_user(to, from, n);
+#endif
 }
 
 extern unsigned long __must_check
diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c
index d72b90905132..588bbc288396 100644
--- a/arch/arm/lib/uaccess_with_memcpy.c
+++ b/arch/arm/lib/uaccess_with_memcpy.c
@@ -88,6 +88,7 @@ pin_page_for_write(const void __user *_addr, pte_t **ptep, spinlock_t **ptlp)
 static unsigned long noinline
 __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
 {
+        unsigned long ua_flags;
         int atomic;
 
         if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
@@ -118,7 +119,9 @@ __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
                 if (tocopy > n)
                         tocopy = n;
 
+                ua_flags = uaccess_save_and_enable();
                 memcpy((void *)to, from, tocopy);
+                uaccess_restore(ua_flags);
                 to += tocopy;
                 from += tocopy;
                 n -= tocopy;
@@ -145,14 +148,21 @@ arm_copy_to_user(void __user *to, const void *from, unsigned long n)
          * With frame pointer disabled, tail call optimization kicks in
          * as well making this test almost invisible.
          */
-        if (n < 64)
-                return __copy_to_user_std(to, from, n);
-        return __copy_to_user_memcpy(to, from, n);
+        if (n < 64) {
+                unsigned long ua_flags = uaccess_save_and_enable();
+                n = __copy_to_user_std(to, from, n);
+                uaccess_restore(ua_flags);
+        } else {
+                n = __copy_to_user_memcpy(to, from, n);
+        }
+        return n;
 }
         
 static unsigned long noinline
 __clear_user_memset(void __user *addr, unsigned long n)
 {
+        unsigned long ua_flags;
+
         if (unlikely(segment_eq(get_fs(), KERNEL_DS))) {
                 memset((void *)addr, 0, n);
                 return 0;
@@ -175,7 +185,9 @@ __clear_user_memset(void __user *addr, unsigned long n)
                 if (tocopy > n)
                         tocopy = n;
 
+                ua_flags = uaccess_save_and_enable();
                 memset((void *)addr, 0, tocopy);
+                uaccess_restore(ua_flags);
                 addr += tocopy;
                 n -= tocopy;
 
@@ -193,9 +205,14 @@ out:
 unsigned long arm_clear_user(void __user *addr, unsigned long n)
 {
         /* See rational for this in __copy_to_user() above. */
-        if (n < 64)
-                return __clear_user_std(addr, n);
-        return __clear_user_memset(addr, n);
+        if (n < 64) {
+                unsigned long ua_flags = uaccess_save_and_enable();
+                n = __clear_user_std(addr, n);
+                uaccess_restore(ua_flags);
+        } else {
+                n = __clear_user_memset(addr, n);
+        }
+        return n;
 }
 
 #if 0