Verify that pmalloc read-only protection is in place: trying to
overwrite a protected variable will crash the kernel.

Signed-off-by: Igor Stoppa <redacted>
---
  drivers/misc/lkdtm.h       |  1 +
  drivers/misc/lkdtm_core.c  |  3 +++
  drivers/misc/lkdtm_perms.c | 28 ++++++++++++++++++++++++++++
  3 files changed, 32 insertions(+)

diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h
index 9e513dcfd809..dcda3ae76ceb 100644
--- a/drivers/misc/lkdtm.h
+++ b/drivers/misc/lkdtm.h

@@ -38,6 +38,7 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void);
  void __init lkdtm_perms_init(void);
  void lkdtm_WRITE_RO(void);
  void lkdtm_WRITE_RO_AFTER_INIT(void);
+void lkdtm_WRITE_RO_PMALLOC(void);

  void lkdtm_WRITE_KERN(void);
  void lkdtm_EXEC_DATA(void);
  void lkdtm_EXEC_STACK(void);

diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
index 2154d1bfd18b..c9fd42bda6ee 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c

@@ -155,6 +155,9 @@ static const struct crashtype crashtypes[] = {
  	CRASHTYPE(ACCESS_USERSPACE),
  	CRASHTYPE(WRITE_RO),
  	CRASHTYPE(WRITE_RO_AFTER_INIT),
+#ifdef CONFIG_PROTECTABLE_MEMORY
+	CRASHTYPE(WRITE_RO_PMALLOC),
+#endif
  	CRASHTYPE(WRITE_KERN),
  	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
  	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),

diff --git a/drivers/misc/lkdtm_perms.c b/drivers/misc/lkdtm_perms.c
index 53b85c9d16b8..0ac9023fd2b0 100644
--- a/drivers/misc/lkdtm_perms.c
+++ b/drivers/misc/lkdtm_perms.c

@@ -9,6 +9,7 @@
  #include <linux/vmalloc.h>
  #include <linux/mman.h>
  #include <linux/uaccess.h>
+#include <linux/pmalloc.h>
  #include <asm/cacheflush.h>
  
  /* Whether or not to fill the target memory area with do_nothing(). */

@@ -104,6 +105,33 @@ void lkdtm_WRITE_RO_AFTER_INIT(void)
  	*ptr ^= 0xabcd1234;
  }
  
+#ifdef CONFIG_PROTECTABLE_MEMORY
+void lkdtm_WRITE_RO_PMALLOC(void)
+{
+	struct gen_pool *pool;
+	int *i;
+
+	pool = pmalloc_create_pool("pool", 0);
+	if (unlikely(!pool)) {
+		pr_info("Failed preparing pool for pmalloc test.");
+		return;
+	}
+
+	i = (int *)pmalloc(pool, sizeof(int), GFP_KERNEL);
+	if (unlikely(!i)) {
+		pr_info("Failed allocating memory for pmalloc test.");
+		pmalloc_destroy_pool(pool);
+		return;
+	}
+
+	*i = INT_MAX;
+	pmalloc_protect_pool(pool);
+
+	pr_info("attempting bad pmalloc write at %p\n", i);
+	*i = 0;