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authorNathan Lynch <nathan_lynch@mentor.com>2014-09-22 22:12:35 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-09-26 14:40:01 +0100
commit389522b0c0530658eb9f9a53410ec2494616d785 (patch)
tree3396e343bf52ab5170d6dda500e053cfde8373c6 /arch/arm/kernel/process.c
parent02e0409a65560da66a747d2ac6023715b04659ea (diff)
downloadlinux-389522b0c0530658eb9f9a53410ec2494616d785.tar.bz2
ARM: 8155/1: place sigpage at a random offset above stack
The sigpage is currently placed alongside shared libraries etc in the address space. Similar to what x86_64 does for its VDSO, place the sigpage at a randomized offset above the stack so that learning the base address of the sigpage doesn't help expose where shared libraries are loaded in the address space (and vice versa). Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/process.c')
-rw-r--r--arch/arm/kernel/process.c37
1 files changed, 36 insertions, 1 deletions
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 46fbbb3701a0..edd2ac3d7c44 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -475,6 +475,39 @@ const char *arch_vma_name(struct vm_area_struct *vma)
return is_gate_vma(vma) ? "[vectors]" : NULL;
}
+/* If possible, provide a placement hint at a random offset from the
+ * stack for the signal page.
+ */
+static unsigned long sigpage_addr(const struct mm_struct *mm,
+ unsigned int npages)
+{
+ unsigned long offset;
+ unsigned long first;
+ unsigned long last;
+ unsigned long addr;
+ unsigned int slots;
+
+ first = PAGE_ALIGN(mm->start_stack);
+
+ last = TASK_SIZE - (npages << PAGE_SHIFT);
+
+ /* No room after stack? */
+ if (first > last)
+ return 0;
+
+ /* Just enough room? */
+ if (first == last)
+ return first;
+
+ slots = ((last - first) >> PAGE_SHIFT) + 1;
+
+ offset = get_random_int() % slots;
+
+ addr = first + (offset << PAGE_SHIFT);
+
+ return addr;
+}
+
static struct page *signal_page;
extern struct page *get_signal_page(void);
@@ -488,6 +521,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long addr;
+ unsigned long hint;
int ret = 0;
if (!signal_page)
@@ -496,7 +530,8 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
return -ENOMEM;
down_write(&mm->mmap_sem);
- addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
+ hint = sigpage_addr(mm, 1);
+ addr = get_unmapped_area(NULL, hint, PAGE_SIZE, 0, 0);
if (IS_ERR_VALUE(addr)) {
ret = addr;
goto up_fail;