[PATCH 09/10] mm: Prevent madvise from changing shadow stack

From: Yu-cheng Yu
Date: Thu Jun 07 2018 - 11:42:13 EST

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx>
---
mm/madvise.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/mm/madvise.c b/mm/madvise.c
index 4d3c922ea1a1..2a6988badd6b 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -839,6 +839,14 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
if (vma && start > vma->vm_start)
prev = vma;

+ /*
+ * Don't do anything on shadow stack.
+ */
+ if (vma->vm_flags & VM_SHSTK) {
+ error = -EINVAL;
+ goto out_no_plug;
+ }
+
blk_start_plug(&plug);
for (;;) {
/* Still start < end. */
@@ -876,6 +884,7 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
}
out:
blk_finish_plug(&plug);
+out_no_plug:
if (write)
up_write(&current->mm->mmap_sem);
else
--
2.15.1