[PATCH v2 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately

[Andy Lutomirski <luto@kernel.org>]

It's currently only used in the EFI code, which is safe AFAICT.
Warn if anyone tries to use it on the normal kernel pgd.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/mm/pageattr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 6a8026918bf6..e9b9c5cedbb8 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1996,6 +1996,9 @@ out:
 void kernel_unmap_pages_in_pgd(pgd_t *root, unsigned long address,
 			       unsigned numpages)
 {
+	/* Unmapping kernel entries from init_mm's pgd is not allowed. */
+	WARN_ON(root == init_mm.pgd);
+
 	unmap_pgd_range(root, address, address + (numpages << PAGE_SHIFT));
 }
 
-- 
2.5.5