x86: remove __range_not_ok()

The __range_not_ok() helper is an x86 (and sparc64) specific interface
that does roughly the same thing as __access_ok(), but with different
calling conventions.

Change this to use the normal interface in order for consistency as we
clean up all access_ok() implementations.

This changes the limit from TASK_SIZE to TASK_SIZE_MAX, which Al points
out is the right thing do do here anyway.

The callers have to use __access_ok() instead of the normal access_ok()
though, because on x86 that contains a WARN_ON_IN_IRQ() check that cannot
be used inside of NMI context while tracing.

The check in copy_code() is not needed any more, because this one is
already done by copy_from_user_nmi().
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Link: https://lore.kernel.org/lkml/YgsUKcXGR7r4nINj@zeniv-ca.linux.org.uk/Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/x86/events/core.c

@@ -2794,7 +2794,7 @@ perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *re
 static inline int
 valid_user_frame(const void __user *fp, unsigned long size)
 {
-	return (__range_not_ok(fp, size, TASK_SIZE) == 0);
+	return __access_ok(fp, size);
 }
 
 static unsigned long get_segment_base(unsigned int segment)

arch/x86/include/asm/uaccess.h

@@ -16,8 +16,10 @@
  * Test whether a block of memory is a valid user space address.
  * Returns 0 if the range is valid, nonzero otherwise.
  */
-static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)
+static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size)
 {
+	unsigned long limit = TASK_SIZE_MAX;
+
 	/*
 	 * If we have used "sizeof()" for the size,
 	 * we know it won't overflow the limit (but
@@ -35,10 +37,10 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
 	return unlikely(addr > limit);
 }
 
-#define __range_not_ok(addr, size, limit)				\
+#define __access_ok(addr, size)						\
 ({									\
 	__chk_user_ptr(addr);						\
-	__chk_range_not_ok((unsigned long __force)(addr), size, limit); \
+	!__chk_range_not_ok((unsigned long __force)(addr), size);	\
 })
 
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
@@ -69,7 +71,7 @@ static inline bool pagefault_disabled(void);
 #define access_ok(addr, size)					\
 ({									\
 	WARN_ON_IN_IRQ();						\
-	likely(!__range_not_ok(addr, size, TASK_SIZE_MAX));		\
+	likely(__access_ok(addr, size));				\
 })
 
 extern int __get_user_1(void);

arch/x86/kernel/dumpstack.c

@@ -81,12 +81,6 @@ static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src,
 	/* The user space code from other tasks cannot be accessed. */
 	if (regs != task_pt_regs(current))
 		return -EPERM;
-	/*
-	 * Make sure userspace isn't trying to trick us into dumping kernel
-	 * memory by pointing the userspace instruction pointer at it.
-	 */
-	if (__chk_range_not_ok(src, nbytes, TASK_SIZE_MAX))
-		return -EINVAL;
 
 	/*
 	 * Even if named copy_from_user_nmi() this can be invoked from

arch/x86/kernel/stacktrace.c

@@ -90,7 +90,7 @@ copy_stack_frame(const struct stack_frame_user __user *fp,
 {
 	int ret;
 
-	if (__range_not_ok(fp, sizeof(*frame), TASK_SIZE))
+	if (!__access_ok(fp, sizeof(*frame)))
 		return 0;
 
 	ret = 1;

arch/x86/lib/usercopy.c

@@ -32,7 +32,7 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
 {
 	unsigned long ret;
 
-	if (__range_not_ok(from, n, TASK_SIZE))
+	if (!__access_ok(from, n))
 		return n;
 
 	if (!nmi_uaccess_okay())