x86 get_unmapped_area(): use proper mmap base for bottom-up direction

commit df54d6fa54275ce59660453e29d1228c2b45a826 upstream.

When the stack is set to unlimited, the bottomup direction is used for
mmap-ings but the mmap_base is not used and thus effectively renders
ASLR for mmapings along with PIE useless.

Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Adrian Sendroiu <molecula2788@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index dbded5aedb818d511a46967ccb1d26d77233110f..48f8375e4c6b07edfbcefd819a8210f6e0839dfe 100644 (file)
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -101,7 +101,7 @@ static void find_start_end(unsigned long flags, unsigned long *begin,
                                *begin = new_begin;
                }
        } else {
-               *begin = TASK_UNMAPPED_BASE;
+               *begin = mmap_legacy_base();
                *end = TASK_SIZE;
        }
 }

diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 845df6835f9ff5fc216ab01857100d41eba77fbf..c1af32385ab100343d791060d02adaabcbd60328 100644 (file)
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -98,7 +98,7 @@ static unsigned long mmap_base(void)
  * Bottom-up (legacy) layout on X86_32 did not support randomization, X86_64
  * does, but not when emulating X86_32
  */
-static unsigned long mmap_legacy_base(void)
+unsigned long mmap_legacy_base(void)
 {
        if (mmap_is_ia32())
                return TASK_UNMAPPED_BASE;

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 178a8d909f14a3dcdcbc0ce255572975c8b3b221..3aeb14b062428250dbcb495220df33822176eda0 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -314,6 +314,7 @@ struct nsproxy;
 struct user_namespace;
 
 #ifdef CONFIG_MMU
+extern unsigned long mmap_legacy_base(void);
 extern void arch_pick_mmap_layout(struct mm_struct *mm);
 extern unsigned long
 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,