[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>

2 files changed, 6 insertions, 12 deletions

diff --git a/arch/um/kernel/skas/include/uaccess-skas.h b/arch/um/kernel/skas/include/uaccess-skas.h
index 7da0c2def0e..f611f83ad4f 100644
--- a/arch/um/kernel/skas/include/uaccess-skas.h
+++ b/arch/um/kernel/skas/include/uaccess-skas.h
@@ -9,14 +9,8 @@
 #include "asm/errno.h"
 #include "asm/fixmap.h"
 
-#define access_ok_skas(type, addr, size) \
-	((segment_eq(get_fs(), KERNEL_DS)) || \
-	 (((unsigned long) (addr) < TASK_SIZE) && \
-	  ((unsigned long) (addr) + (size) <= TASK_SIZE)) || \
-	 ((type == VERIFY_READ ) && \
-	  ((unsigned long) (addr) >= FIXADDR_USER_START) && \
-	  ((unsigned long) (addr) + (size) <= FIXADDR_USER_END) && \
-	  ((unsigned long) (addr) + (size) >= (unsigned long)(addr))))
+/* No SKAS-specific checking. */
+#define access_ok_skas(type, addr, size) 0
 
 extern int copy_from_user_skas(void *to, const void __user *from, int n);
 extern int copy_to_user_skas(void __user *to, const void *from, int n);
diff --git a/arch/um/kernel/skas/uaccess.c b/arch/um/kernel/skas/uaccess.c
index 75195281081..a5a47528dec 100644
--- a/arch/um/kernel/skas/uaccess.c
+++ b/arch/um/kernel/skas/uaccess.c
@@ -143,7 +143,7 @@ int copy_from_user_skas(void *to, const void __user *from, int n)
 		return(0);
 	}
 
-	return(access_ok_skas(VERIFY_READ, from, n) ?
+	return(access_ok(VERIFY_READ, from, n) ?
 	       buffer_op((unsigned long) from, n, 0, copy_chunk_from_user, &to):
 	       n);
 }
@@ -164,7 +164,7 @@ int copy_to_user_skas(void __user *to, const void *from, int n)
 		return(0);
 	}
 
-	return(access_ok_skas(VERIFY_WRITE, to, n) ?
+	return(access_ok(VERIFY_WRITE, to, n) ?
 	       buffer_op((unsigned long) to, n, 1, copy_chunk_to_user, &from) :
 	       n);
 }
@@ -193,7 +193,7 @@ int strncpy_from_user_skas(char *dst, const char __user *src, int count)
 		return(strnlen(dst, count));
 	}
 
-	if(!access_ok_skas(VERIFY_READ, src, 1))
+	if(!access_ok(VERIFY_READ, src, 1))
 		return(-EFAULT);
 
 	n = buffer_op((unsigned long) src, count, 0, strncpy_chunk_from_user,
@@ -221,7 +221,7 @@ int clear_user_skas(void __user *mem, int len)
 		return(0);
 	}
 
-	return(access_ok_skas(VERIFY_WRITE, mem, len) ?
+	return(access_ok(VERIFY_WRITE, mem, len) ?
 	       buffer_op((unsigned long) mem, len, 1, clear_chunk, NULL) : len);
 }