x86/mm/fault: Use TASK_SIZE_MAX in is_prefetch()

This is slightly shorter and slightly faster.  It's also more
correct: the split between user and kernel addresses is
TASK_SIZE_MAX, regardless of ti->flags.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/09156b63bad90a327827003c9e53faa82ef4c56e.1426728647.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index ede025f..ae340d3 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -148,7 +148,7 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
        instr = (void *)convert_ip_to_linear(current, regs);
        max_instr = instr + 15;
 
-       if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
+       if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
                return 0;
 
        while (instr < max_instr) {