ARM: move signal handlers into a vdso-like page
Move the signal handlers into a VDSO page rather than keeping them in
the vectors page. This allows us to place them randomly within this
page, and also map the page at a random location within userspace
further protecting these code fragments from ROP attacks. The new
VDSO page is also poisoned in the same way as the vector page.
Change-Id: Ic45bb26efb1f00de0a025d36fc15dbd6580dc7de
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Git-commit: 48be69a026b2c17350a5ef18a1959a919f60be7d
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[joonwoop@codeaurora.org: fixed merge conflict]
CRs-fixed: 561044
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index e8881bb..de9a39c 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -675,8 +675,8 @@
#ifdef CONFIG_MMU
/*
* The vectors page is always readable from user space for the
- * atomic helpers and the signal restart code. Insert it into the
- * gate_vma so that it is visible through ptrace and /proc/<pid>/mem.
+ * atomic helpers. Insert it into the gate_vma so that it is visible
+ * through ptrace and /proc/<pid>/mem.
*/
static struct vm_area_struct gate_vma;
@@ -710,9 +710,43 @@
{
if (vma == &gate_vma)
return "[vectors]";
+ else if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.sigpage)
+ return "[sigpage]";
else if (vma == get_user_timers_vma(NULL))
return "[timers]";
else
return NULL;
}
+
+extern struct page *get_signal_page(void);
+
+int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
+{
+ struct mm_struct *mm = current->mm;
+ struct page *page;
+ unsigned long addr;
+ int ret;
+
+ page = get_signal_page();
+ if (!page)
+ return -ENOMEM;
+
+ down_write(&mm->mmap_sem);
+ addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
+ if (IS_ERR_VALUE(addr)) {
+ ret = addr;
+ goto up_fail;
+ }
+
+ ret = install_special_mapping(mm, addr, PAGE_SIZE,
+ VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
+ &page);
+
+ if (ret == 0)
+ mm->context.sigpage = addr;
+
+ up_fail:
+ up_write(&mm->mmap_sem);
+ return ret;
+}
#endif