compat_{get,put}_bitmap(): use unsafe_{get,put}_user()

unroll the inner loops, while we are at it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 29 insertions, 55 deletions

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 1c5f3152cbb5..94ceb0348a25 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -388,8 +388,7 @@ asmlinkage long compat_sys_wait4(compat_pid_t pid,
 
 #define BITS_PER_COMPAT_LONG    (8*sizeof(compat_long_t))
 
-#define BITS_TO_COMPAT_LONGS(bits) \
-        (((bits)+BITS_PER_COMPAT_LONG-1)/BITS_PER_COMPAT_LONG)
+#define BITS_TO_COMPAT_LONGS(bits) DIV_ROUND_UP(bits, BITS_PER_COMPAT_LONG)
 
 long compat_get_bitmap(unsigned long *mask, const compat_ulong_t __user *umask,
                        unsigned long bitmap_size);
diff --git a/kernel/compat.c b/kernel/compat.c
index 860f674fa556..9c2a8f3788d5 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -871,84 +871,59 @@ int get_compat_sigevent(struct sigevent *event,
 long compat_get_bitmap(unsigned long *mask, const compat_ulong_t __user *umask,
                        unsigned long bitmap_size)
 {
-        int i, j;
-        unsigned long m;
-        compat_ulong_t um;
         unsigned long nr_compat_longs;
 
         /* align bitmap up to nearest compat_long_t boundary */
         bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
+        nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
 
         if (!access_ok(VERIFY_READ, umask, bitmap_size / 8))
                 return -EFAULT;
 
-        nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
-
-        for (i = 0; i < BITS_TO_LONGS(bitmap_size); i++) {
-                m = 0;
-
-                for (j = 0; j < sizeof(m)/sizeof(um); j++) {
-                        /*
-                         * We dont want to read past the end of the userspace
-                         * bitmap. We must however ensure the end of the
-                         * kernel bitmap is zeroed.
-                         */
-                        if (nr_compat_longs) {
-                                nr_compat_longs--;
-                                if (__get_user(um, umask))
-                                        return -EFAULT;
-                        } else {
-                                um = 0;
-                        }
-
-                        umask++;
-                        m |= (long)um << (j * BITS_PER_COMPAT_LONG);
-                }
-                *mask++ = m;
+        user_access_begin();
+        while (nr_compat_longs > 1) {
+                compat_ulong_t l1, l2;
+                unsafe_get_user(l1, umask++, Efault);
+                unsafe_get_user(l2, umask++, Efault);
+                *mask++ = ((unsigned long)l2 << BITS_PER_COMPAT_LONG) | l1;
+                nr_compat_longs -= 2;
         }
-
+        if (nr_compat_longs)
+                unsafe_get_user(*mask, umask++, Efault);
+        user_access_end();
         return 0;
+
+Efault:
+        user_access_end();
+        return -EFAULT;
 }
 
 long compat_put_bitmap(compat_ulong_t __user *umask, unsigned long *mask,
                        unsigned long bitmap_size)
 {
-        int i, j;
-        unsigned long m;
-        compat_ulong_t um;
         unsigned long nr_compat_longs;
 
         /* align bitmap up to nearest compat_long_t boundary */
         bitmap_size = ALIGN(bitmap_size, BITS_PER_COMPAT_LONG);
+        nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
 
         if (!access_ok(VERIFY_WRITE, umask, bitmap_size / 8))
                 return -EFAULT;
 
-        nr_compat_longs = BITS_TO_COMPAT_LONGS(bitmap_size);
-
-        for (i = 0; i < BITS_TO_LONGS(bitmap_size); i++) {
-                m = *mask++;
-
-                for (j = 0; j < sizeof(m)/sizeof(um); j++) {
-                        um = m;
-
-                        /*
-                         * We dont want to write past the end of the userspace
-                         * bitmap.
-                         */
-                        if (nr_compat_longs) {
-                                nr_compat_longs--;
-                                if (__put_user(um, umask))
-                                        return -EFAULT;
-                        }
-
-                        umask++;
-                        m >>= 4*sizeof(um);
-                        m >>= 4*sizeof(um);
-                }
+        user_access_begin();
+        while (nr_compat_longs > 1) {
+                unsigned long m = *mask++;
+                unsafe_put_user((compat_ulong_t)m, umask++, Efault);
+                unsafe_put_user(m >> BITS_PER_COMPAT_LONG, umask++, Efault);
+                nr_compat_longs -= 2;
         }
-
+        if (nr_compat_longs)
+                unsafe_put_user((compat_ulong_t)*mask, umask++, Efault);
+        user_access_end();
         return 0;
+Efault:
+        user_access_end();
+        return -EFAULT;
 }
 
 void