[PATCH v6 3/4] fanotify: introduce new event mask FAN_OPEN_EXEC_PERM

[Matthew Bobrowski <mbobrowski@mbobrowski.org>]

A new event mask FAN_OPEN_EXEC_PERM has been defined. This allows users
to receive events and grant acccess 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 manner as previous permission event types, meaning
that an access response is required from the application to permit any
further operations on the file. This feature is implemented within the
fsnotify_perm() hook by setting the 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         | 12 +++++++-----
 include/linux/fsnotify_backend.h | 10 ++++++----
 include/uapi/linux/fanotify.h    |  1 +
 6 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index e30f3a1d9699..d9aa505591eb 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -210,8 +210,9 @@ 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 b3f58f36a0ab..ecf09b6243d9 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -401,7 +401,7 @@ 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 c521e4264f2b..9e2142795335 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -40,7 +40,8 @@
 				 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..9c7b594bf540 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -26,7 +26,7 @@ static inline int fsnotify_parent(const struct path *path, struct dentry *dentry
 	return __fsnotify_parent(path, dentry, mask);
 }
 
-/* simple call site for access decisions */
+/* Simple call site for access decisions */
 static inline int fsnotify_perm(struct file *file, int mask)
 {
 	const struct path *path = &file->f_path;
@@ -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 39d94e62a836..150c0acb2f43 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 event 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 */
@@ -64,11 +65,12 @@
 				   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)
 
-#define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM)
+#define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM | \
+				  FS_OPEN_EXEC_PERM)
 
 /* Events that can be reported to backends */
 #define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
@@ -77,7 +79,7 @@
 			     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 d9664fbc905b..909c98fcace2 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


-- 
Matthew Bobrowski