[PATCH v5 3/3] fanotify: introduce new event type FAN_OPEN_EXEC_PERM

[Matthew Bobrowski <mbobrowski@mbobrowski.org>]

A new event type FAN_OPEN_EXEC_PERM has been defined. This allows users
to receive and grant access to files that are intending to be opened for
execution. Events of FAN_OPEN_EXEC_PERM type will be generated when a file
has been opened by using either execve(), execveat() or uselib() system
calls.

This acts in the same manor as previous permission event types, meaning
that an access response is required from the application to permit
further operations on the file. This feature is implemented within the
fsnotify_perm() hook by setting FAN_OPEN_EXEC_PERM event type if
__FMODE_EXEC is set within file->f_flags.

Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
---
 fs/notify/fanotify/fanotify.c    |  3 ++-
 fs/notify/fsnotify.c             |  2 +-
 include/linux/fanotify.h         |  3 ++-
 include/linux/fsnotify.h         | 10 ++++++----
 include/linux/fsnotify_backend.h |  7 ++++---
 include/uapi/linux/fanotify.h    |  1 +
 6 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 8a49a0adab73..a427daf8d117 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -211,8 +211,9 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
 	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
 	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
+	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 11);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 12);
 
 	mask = fanotify_group_event_mask(iter_info, mask, data, data_type);
 	if (!mask)
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 051e5fc0dba1..40ed97aede29 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -402,7 +402,7 @@ static __init int fsnotify_init(void)
 {
 	int ret;
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 24);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);
 
 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 0e07d23b6c17..614943153596 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -42,7 +42,8 @@
 				 FAN_CLOSE | FAN_OPEN | FAN_OPEN_EXEC)
 
 /* Events that require a permission response from user */
-#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)
+#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM | \
+				 FAN_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define FANOTIFY_EVENT_FLAGS	(FAN_EVENT_ON_CHILD | FAN_ONDIR)
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 1fe5ac93b252..6fb8d1fcfeaf 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -38,12 +38,14 @@ static inline int fsnotify_perm(struct file *file, int mask)
 		return 0;
 	if (!(mask & (MAY_READ | MAY_OPEN)))
 		return 0;
-	if (mask & MAY_OPEN)
+	if (mask & MAY_OPEN) {
 		fsnotify_mask = FS_OPEN_PERM;
-	else if (mask & MAY_READ)
+
+		if (file->f_flags & __FMODE_EXEC)
+			fsnotify_mask |= FS_OPEN_EXEC_PERM;
+	} else if (mask & MAY_READ) {
 		fsnotify_mask = FS_ACCESS_PERM;
-	else
-		BUG();
+	}
 
 	ret = fsnotify_parent(path, NULL, fsnotify_mask);
 	if (ret)
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 329ac6684326..96616651220c 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -44,8 +44,9 @@
 #define FS_Q_OVERFLOW		0x00004000	/* Event queued overflowed */
 #define FS_IN_IGNORED		0x00008000	/* last inotify event here */
 
-#define FS_OPEN_PERM		0x00010000	/* open event in an permission hook */
+#define FS_OPEN_PERM		0x00010000	/* open event in a permission hook */
 #define FS_ACCESS_PERM		0x00020000	/* access event in a permissions hook */
+#define FS_OPEN_EXEC_PERM	0x00040000	/* open/exec in a permission hook */
 
 #define FS_EXCL_UNLINK		0x04000000	/* do not send events if object is unlinked */
 #define FS_ISDIR		0x40000000	/* event occurred against dir */
@@ -64,7 +65,7 @@
 				   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN |\
 				   FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE |\
 				   FS_DELETE | FS_OPEN_PERM | FS_ACCESS_PERM |\
-				   FS_OPEN_EXEC)
+				   FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 #define FS_MOVE			(FS_MOVED_FROM | FS_MOVED_TO)
 
@@ -77,7 +78,7 @@
 			     FS_DELETE | FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
 			     FS_OPEN_PERM | FS_ACCESS_PERM | FS_DN_RENAME |\
-			     FS_OPEN_EXEC)
+			     FS_OPEN_EXEC | FS_OPEN_EXEC_PERM)
 
 /* Extra flags that may be reported with event or control handling of events */
 #define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index da278f11ab29..e2df10c61cb1 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -16,6 +16,7 @@
 
 #define FAN_OPEN_PERM		0x00010000	/* File open in perm check */
 #define FAN_ACCESS_PERM		0x00020000	/* File accessed in perm check */
+#define FAN_OPEN_EXEC_PERM	0x00040000	/* File open/exec in perm check */
 
 #define FAN_ONDIR		0x40000000	/* event occurred against dir */
 
-- 
2.17.2