From: Radu Caragea <sinaelgl@xxxxxxxxx>
Subject: x86 get_unmapped_area(): use proper mmap base for bottom-up direction
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.
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Adrian Sendroiu <molecula2788@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/sys_x86_64.c | 2 +-
arch/x86/mm/mmap.c | 2 +-
include/linux/sched.h | 1 +
3 files changed, 3 insertions(+), 2 deletions(-)
diff -puN arch/x86/kernel/sys_x86_64.c~x86-get_unmapped_area-use-proper-mmap-base-for-bottom-up-direction arch/x86/kernel/sys_x86_64.c
--- a/arch/x86/kernel/sys_x86_64.c~x86-get_unmapped_area-use-proper-mmap-base-for-bottom-up-direction
+++ a/arch/x86/kernel/sys_x86_64.c
@@ -101,7 +101,7 @@ static void find_start_end(unsigned long
*begin = new_begin;
}
} else {
- *begin = TASK_UNMAPPED_BASE;
+ *begin = mmap_legacy_base();
*end = TASK_SIZE;
}
}
diff -puN arch/x86/mm/mmap.c~x86-get_unmapped_area-use-proper-mmap-base-for-bottom-up-direction arch/x86/mm/mmap.c
--- a/arch/x86/mm/mmap.c~x86-get_unmapped_area-use-proper-mmap-base-for-bottom-up-direction
+++ a/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 -puN include/linux/sched.h~x86-get_unmapped_area-use-proper-mmap-base-for-bottom-up-direction include/linux/sched.h
--- a/include/linux/sched.h~x86-get_unmapped_area-use-proper-mmap-base-for-bottom-up-direction
+++ a/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,
_
--
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