[PATCH v9 7/9] PM: hibernate: disable when there are active secretmem users

[Mike Rapoport <rppt@xxxxxxxxxx>]

From: Mike Rapoport <rppt@xxxxxxxxxxxxx>

It is unsafe to allow saving of secretmem areas to the hibernation snapshot
as they would be visible after the resume and this essentially will defeat
the purpose of secret memory mappings.

Prevent hibernation whenever there are active secret memory users.

Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
---
 include/linux/secretmem.h |  6 ++++++
 kernel/power/hibernate.c  |  5 ++++-
 mm/secretmem.c            | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
index 70e7db9f94fe..907a6734059c 100644
--- a/include/linux/secretmem.h
+++ b/include/linux/secretmem.h
@@ -6,6 +6,7 @@
 
 bool vma_is_secretmem(struct vm_area_struct *vma);
 bool page_is_secretmem(struct page *page);
+bool secretmem_active(void);
 
 #else
 
@@ -19,6 +20,11 @@ static inline bool page_is_secretmem(struct page *page)
 	return false;
 }
 
+static inline bool secretmem_active(void)
+{
+	return false;
+}
+
 #endif /* CONFIG_SECRETMEM */
 
 #endif /* _LINUX_SECRETMEM_H */
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index da0b41914177..559acef3fddb 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -31,6 +31,7 @@
 #include <linux/genhd.h>
 #include <linux/ktime.h>
 #include <linux/security.h>
+#include <linux/secretmem.h>
 #include <trace/events/power.h>
 
 #include "power.h"
@@ -81,7 +82,9 @@ void hibernate_release(void)
 
 bool hibernation_available(void)
 {
-	return nohibernate == 0 && !security_locked_down(LOCKDOWN_HIBERNATION);
+	return nohibernate == 0 &&
+		!security_locked_down(LOCKDOWN_HIBERNATION) &&
+		!secretmem_active();
 }
 
 /**
diff --git a/mm/secretmem.c b/mm/secretmem.c
index abf6ecdf70cb..14ef439841c9 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -51,6 +51,13 @@ struct secretmem_ctx {
 
 static struct cma *secretmem_cma;
 
+static atomic_t secretmem_users;
+
+bool secretmem_active(void)
+{
+	return !!atomic_read(&secretmem_users);
+}
+
 static int secretmem_account_pages(struct page *page, gfp_t gfp, int order)
 {
 	int err;
@@ -185,6 +192,12 @@ static const struct vm_operations_struct secretmem_vm_ops = {
 	.fault = secretmem_fault,
 };
 
+static int secretmem_release(struct inode *inode, struct file *file)
+{
+	atomic_dec(&secretmem_users);
+	return 0;
+}
+
 static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct secretmem_ctx *ctx = file->private_data;
@@ -211,6 +224,7 @@ bool vma_is_secretmem(struct vm_area_struct *vma)
 }
 
 static const struct file_operations secretmem_fops = {
+	.release	= secretmem_release,
 	.mmap		= secretmem_mmap,
 };
 
@@ -328,6 +342,7 @@ SYSCALL_DEFINE1(memfd_secret, unsigned long, flags)
 	file->f_flags |= O_LARGEFILE;
 
 	fd_install(fd, file);
+	atomic_inc(&secretmem_users);
 	return fd;
 
 err_put_fd:
-- 
2.28.0