FAN_REPORT_FID is ambiguous in that it reports the fid of the child for
some events and the fid of the parent for create/delete/move events.
The new FAN_REPORT_TARGET_FID flag is an implicit request to report
the fid of the target object of the operation (a.k.a the child inode)
also in create/delete/move events in addition to the fid of the parent
and the name of the child.
To reduce the test matrix for uninteresting use cases, the new
FAN_REPORT_TARGET_FID flag requires both FAN_REPORT_NAME and
FAN_REPORT_FID. The convenience macro FAN_REPORT_ALL_FIDS combines
FAN_REPORT_TARGET_FID with all the required flags.
The new flag is not yet enabled in this change.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/notify/fanotify/fanotify.c | 48 ++++++++++++++++++++++--------
fs/notify/fanotify/fanotify_user.c | 9 ++++++
include/uapi/linux/fanotify.h | 4 +++
3 files changed, 49 insertions(+), 12 deletions(-)
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index b6091775aa6e..9b1641ecfe97 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -458,17 +458,41 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
}
/*
- * The inode to use as identifier when reporting fid depends on the event.
- * Report the modified directory inode on dirent modification events.
- * Report the "victim" inode otherwise.
+ * FAN_REPORT_FID is ambiguous in that it reports the fid of the child for
+ * some events and the fid of the parent for create/delete/move events.
+ *
+ * With the FAN_REPORT_TARGET_FID flag, the fid of the child is reported
+ * also in create/delete/move events in addition to the fid of the parent
+ * and the name of the child.
+ */
+static inline bool fanotify_report_child_fid(unsigned int fid_mode, u32 mask)
+{
+ if (mask & ALL_FSNOTIFY_DIRENT_EVENTS)
+ return (fid_mode & FAN_REPORT_TARGET_FID);
+
+ return (fid_mode & FAN_REPORT_FID) && !(mask & FAN_ONDIR);
+}
+
+/*
+ * The inode to use as identifier when reporting fid depends on the event
+ * and the group flags.
+ *
+ * With the group flag FAN_REPORT_TARGET_FID, always report the child fid.
+ *
+ * Without the group flag FAN_REPORT_TARGET_FID, report the modified directory
+ * fid on dirent events and the child fid otherwise.
+ *
* For example:
- * FS_ATTRIB reports the child inode even if reported on a watched parent.
- * FS_CREATE reports the modified dir inode and not the created inode.
+ * FS_ATTRIB reports the child fid even if reported on a watched parent.
+ * FS_CREATE reports the modified dir fid without FAN_REPORT_TARGET_FID.
+ * and reports the created child fid with FAN_REPORT_TARGET_FID.
*/
static struct inode *fanotify_fid_inode(u32 event_mask, const void *data,
- int data_type, struct inode *dir)
+ int data_type, struct inode *dir,
+ unsigned int fid_mode)
{
- if (event_mask & ALL_FSNOTIFY_DIRENT_EVENTS)
+ if ((event_mask & ALL_FSNOTIFY_DIRENT_EVENTS) &&
+ !(fid_mode & FAN_REPORT_TARGET_FID))
return dir;
return fsnotify_data_inode(data, data_type);
@@ -647,10 +671,11 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
{
struct fanotify_event *event = NULL;
gfp_t gfp = GFP_KERNEL_ACCOUNT;
- struct inode *id = fanotify_fid_inode(mask, data, data_type, dir);
+ unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
+ struct inode *id = fanotify_fid_inode(mask, data, data_type, dir,
+ fid_mode);
struct inode *dirid = fanotify_dfid_inode(mask, data, data_type, dir);
const struct path *path = fsnotify_data_path(data, data_type);
- unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
struct mem_cgroup *old_memcg;
struct inode *child = NULL;
bool name_event = false;
@@ -660,11 +685,10 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
if ((fid_mode & FAN_REPORT_DIR_FID) && dirid) {
/*
- * With both flags FAN_REPORT_DIR_FID and FAN_REPORT_FID, we
- * report the child fid for events reported on a non-dir child
+ * For certain events and group flags, report the child fid
* in addition to reporting the parent fid and maybe child name.
*/
- if ((fid_mode & FAN_REPORT_FID) && id != dirid && !ondir)
+ if (fanotify_report_child_fid(fid_mode, mask) && id != dirid)
child = id;
id = dirid;
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 559bc1e9926d..6ec26b124041 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1275,6 +1275,15 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
return -EINVAL;
+ /*
+ * FAN_REPORT_TARGET_FID requires FAN_REPORT_NAME and FAN_REPORT_FID
+ * and is used as an indication to report both dir and child fid on all
+ * dirent events.
+ */
+ if ((fid_mode & FAN_REPORT_TARGET_FID) &&
+ (!(fid_mode & FAN_REPORT_NAME) || !(fid_mode & FAN_REPORT_FID)))
+ return -EINVAL;
+
f_flags = O_RDWR | FMODE_NONOTIFY;
if (flags & FAN_CLOEXEC)
f_flags |= O_CLOEXEC;
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index bd1932c2074d..f9202ce31b0d 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -57,9 +57,13 @@
#define FAN_REPORT_FID 0x00000200 /* Report unique file id */
#define FAN_REPORT_DIR_FID 0x00000400 /* Report unique directory id */
#define FAN_REPORT_NAME 0x00000800 /* Report events with name */
+#define FAN_REPORT_TARGET_FID 0x00001000 /* Report dirent target id */
/* Convenience macro - FAN_REPORT_NAME requires FAN_REPORT_DIR_FID */
#define FAN_REPORT_DFID_NAME (FAN_REPORT_DIR_FID | FAN_REPORT_NAME)
+/* Convenience macro - FAN_REPORT_TARGET_FID requires all other FID flags */
+#define FAN_REPORT_ALL_FIDS (FAN_REPORT_DFID_NAME | FAN_REPORT_FID | \
+ FAN_REPORT_TARGET_FID)
/* Deprecated - do not use this in programs and do not add new flags here! */
#define FAN_ALL_INIT_FLAGS (FAN_CLOEXEC | FAN_NONBLOCK | \
--
2.33.1
