[PATCH] uml: fix access_ok

The access_ok_tt() macro is bogus, in that a read access is unconditionally
considered valid.

I couldn't find in SCM logs the introduction of this check, but I went back to
2.4.20-1um and the definition was the same.

Possibly this was done to avoid problems with missing set_fs() calls, but
there can't be any I think because they would fail with SKAS mode.
TT-specific code is still to check.

Also, this patch joins common code together, and makes the "address range
wrapping" check happen for all cases, rather than for only some.

This may, possibly, be reoptimized at some time, but the current code doesn't
seem clever, just confused.

* Important: I've also had to change references to access_ok_{tt,skas} back to
  access_ok - the kernel wasn't that happy otherwise.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 18 insertions, 1 deletions

diff --git a/arch/um/include/um_uaccess.h b/arch/um/include/um_uaccess.h
index 84c0868cd561..f8760a3f43b0 100644
--- a/arch/um/include/um_uaccess.h
+++ b/arch/um/include/um_uaccess.h
@@ -17,8 +17,25 @@
 #include "uaccess-skas.h"
 #endif
 
+#define __under_task_size(addr, size) \
+        (((unsigned long) (addr) < TASK_SIZE) && \
+         (((unsigned long) (addr) + (size)) < TASK_SIZE))
+
+#define __access_ok_vsyscall(type, addr, size) \
+         ((type == VERIFY_READ) && \
+          ((unsigned long) (addr) >= FIXADDR_USER_START) && \
+          ((unsigned long) (addr) + (size) <= FIXADDR_USER_END) && \
+          ((unsigned long) (addr) + (size) >= (unsigned long)(addr)))
+
+#define __addr_range_nowrap(addr, size) \
+        ((unsigned long) (addr) <= ((unsigned long) (addr) + (size)))
+
 #define access_ok(type, addr, size) \
-        CHOOSE_MODE_PROC(access_ok_tt, access_ok_skas, type, addr, size)
+        (__addr_range_nowrap(addr, size) && \
+         (__under_task_size(addr, size) || \
+          __access_ok_vsyscall(type, addr, size) || \
+          segment_eq(get_fs(), KERNEL_DS) || \
+          CHOOSE_MODE_PROC(access_ok_tt, access_ok_skas, type, addr, size)))
 
 static inline int copy_from_user(void *to, const void __user *from, int n)
 {