[PATCH] x86_64: enlarge window for stack growth
Allow stack growth so the 'enter' instruction works. Also
fixes problem in compat_sys_kexec_load() which could allocate
more than 128 bytes using compat_alloc_user_space().
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index 6472889..4968a71 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -410,8 +410,10 @@
if (!(vma->vm_flags & VM_GROWSDOWN))
goto bad_area;
if (error_code & 4) {
- // XXX: align red zone size with ABI
- if (address + 128 < regs->rsp)
+ /* Allow userspace just enough access below the stack pointer
+ * to let the 'enter' instruction work.
+ */
+ if (address + 65536 + 32 * sizeof(unsigned long) < regs->rsp)
goto bad_area;
}
if (expand_stack(vma, address))