[PATCH 3/4] arm64/kprobes: set VM_FLUSH_RESET_PERMS on kprobe instruction pages

[Ard Biesheuvel]

In order to avoid transient inconsistencies where freed code pages
are remapped writable while stale TLB entries still exist on other
cores, mark the kprobes text pages with the VM_FLUSH_RESET_PERMS
attribute. This instructs the core vmalloc code not to defer the
TLB flush when this region is unmapped and returned to the page
allocator.

Signed-off-by: Ard Biesheuvel <ard.biesheu...@arm.com>
---
 arch/arm64/kernel/probes/kprobes.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c 
b/arch/arm64/kernel/probes/kprobes.c
index 2509fcb6d404..036cfbf9682a 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -131,8 +131,10 @@ void *alloc_insn_page(void)
        void *page;
 
        page = vmalloc_exec(PAGE_SIZE);
-       if (page)
+       if (page) {
                set_memory_ro((unsigned long)page, 1);
+               set_vm_flush_reset_perms(page);
+       }
 
        return page;
 }
-- 
2.17.1