[PATCH v3 0/3] New fanotify API for ignoring events

[PATCH v3 0/3] New fanotify API for ignoring events

[Amir Goldstein]

Hi Jan,

As we discussed [1], here is the implementation of the new
FAN_MARK_IGNORE API, to try and sort the historic mess of
FAN_MARK_IGNORED_MASK.

We use the opportunity of the new API to further restict the events
and flags that are allowed in ignore mask of a non-dir inode mark and
we require FAN_MARK_IGNORED_SURV_MODIFY for dir/mount/sb ignore mark
to remove from the test matrix a lot of notsensical combinations.

I extended the LTP tests [2] to cover the bug that you pointed out
in [v1] review. I verified that the 6 relevant test cases fail with
the buggy v1 version and pass in this version.

The man page draft [3] has been updated to reflect the new restrictions,
some of which have already been added by a Fixes patch [4].

Thanks,
Amir.

Changes since [v2]:
- Rebase on top of API restriction patch
- Require FAN_MARK_IGNORED_SURV_MODIFY for dir/mount/sb ignore mark
- Add test coverage and update man page with new restrictions

Changes since [v1]:
- Replace "sticky" semantics with EEXITS error
- Simplify EINVAL checks
- Add missing ignore mask accessors
- Add fsnotify_effective_ignore_mask() helper to fix bug

[v1] https://lore.kernel.org/linux-fsdevel/20220620134551.2066847-1-amir73il@gmail.com/
[v2] https://lore.kernel.org/linux-fsdevel/20220624143538.2500990-1-amir73il@gmail.com/
[1] https://lore.kernel.org/linux-fsdevel/20220428123824.ssq72ovqg2nao5f4@quack3.lan/
[2] https://github.com/amir73il/ltp/commits/fan_mark_ignore
[3] https://github.com/amir73il/man-pages/commits/fan_mark_ignore
[4] https://lore.kernel.org/linux-fsdevel/20220627174719.2838175-1-amir73il@gmail.com/

Amir Goldstein (3):
  fanotify: prepare for setting event flags in ignore mask
  fanotify: cleanups for fanotify_mark() input validations
  fanotify: introduce FAN_MARK_IGNORE

 fs/notify/fanotify/fanotify.c      |  19 ++---
 fs/notify/fanotify/fanotify.h      |   2 +
 fs/notify/fanotify/fanotify_user.c | 110 ++++++++++++++++++++++-------
 fs/notify/fdinfo.c                 |   6 +-
 fs/notify/fsnotify.c               |  21 +++---
 include/linux/fanotify.h           |  14 ++--
 include/linux/fsnotify_backend.h   |  89 +++++++++++++++++++++--
 include/uapi/linux/fanotify.h      |   8 +++
 8 files changed, 212 insertions(+), 57 deletions(-)

-- 
2.25.1

[PATCH v3 1/3] fanotify: prepare for setting event flags in ignore mask

[Amir Goldstein]

Setting flags FAN_ONDIR FAN_EVENT_ON_CHILD in ignore mask has no effect.
The FAN_EVENT_ON_CHILD flag in mask implicitly applies to ignore mask and
ignore mask is always implicitly applied to events on directories.

Define a mark flag that replaces this legacy behavior with logic of
applying the ignore mask according to event flags in ignore mask.

Implement the new logic to prepare for supporting an ignore mask that
ignores events on children and ignore mask that does not ignore events
on directories.

To emphasize the change in terminology, also rename ignored_mask mark
member to ignore_mask and use accessors to get only the effective
ignored events or the ignored events and flags.

This change in terminology finally aligns with the "ignore mask"
language in man pages and in most of the comments.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.c      | 19 ++++---
 fs/notify/fanotify/fanotify_user.c | 21 ++++---
 fs/notify/fdinfo.c                 |  6 +-
 fs/notify/fsnotify.c               | 21 ++++---
 include/linux/fsnotify_backend.h   | 89 ++++++++++++++++++++++++++++--
 5 files changed, 121 insertions(+), 35 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 4f897e109547..cd7d09a569ff 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -295,12 +295,13 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 				     const void *data, int data_type,
 				     struct inode *dir)
 {
-	__u32 marks_mask = 0, marks_ignored_mask = 0;
+	__u32 marks_mask = 0, marks_ignore_mask = 0;
 	__u32 test_mask, user_mask = FANOTIFY_OUTGOING_EVENTS |
 				     FANOTIFY_EVENT_FLAGS;
 	const struct path *path = fsnotify_data_path(data, data_type);
 	unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
 	struct fsnotify_mark *mark;
+	bool ondir = event_mask & FAN_ONDIR;
 	int type;
 
 	pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
@@ -315,19 +316,21 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 			return 0;
 	} else if (!(fid_mode & FAN_REPORT_FID)) {
 		/* Do we have a directory inode to report? */
-		if (!dir && !(event_mask & FS_ISDIR))
+		if (!dir && !ondir)
 			return 0;
 	}
 
 	fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
-		/* Apply ignore mask regardless of mark's ISDIR flag */
-		marks_ignored_mask |= mark->ignored_mask;
+		/*
+		 * Apply ignore mask depending on event flags in ignore mask.
+		 */
+		marks_ignore_mask |=
+			fsnotify_effective_ignore_mask(mark, ondir, type);
 
 		/*
-		 * If the event is on dir and this mark doesn't care about
-		 * events on dir, don't send it!
+		 * Send the event depending on event flags in mark mask.
 		 */
-		if (event_mask & FS_ISDIR && !(mark->mask & FS_ISDIR))
+		if (!fsnotify_mask_applicable(mark->mask, ondir, type))
 			continue;
 
 		marks_mask |= mark->mask;
@@ -336,7 +339,7 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 		*match_mask |= 1U << type;
 	}
 
-	test_mask = event_mask & marks_mask & ~marks_ignored_mask;
+	test_mask = event_mask & marks_mask & ~marks_ignore_mask;
 
 	/*
 	 * For dirent modification events (create/delete/move) that do not carry
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index b08ce0d821a7..a9eea037fee9 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1012,7 +1012,7 @@ static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 	if (!(flags & FAN_MARK_IGNORED_MASK)) {
 		fsn_mark->mask &= ~mask;
 	} else {
-		fsn_mark->ignored_mask &= ~mask;
+		fsn_mark->ignore_mask &= ~mask;
 	}
 	newmask = fsnotify_calc_mask(fsn_mark);
 	/*
@@ -1021,7 +1021,7 @@ static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 	 * changes to the mask.
 	 * Destroy mark when only umask bits remain.
 	 */
-	*destroy = !((fsn_mark->mask | fsn_mark->ignored_mask) & ~umask);
+	*destroy = !((fsn_mark->mask | fsn_mark->ignore_mask) & ~umask);
 	spin_unlock(&fsn_mark->lock);
 
 	return oldmask & ~newmask;
@@ -1090,7 +1090,7 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
 	/*
 	 * Setting FAN_MARK_IGNORED_SURV_MODIFY for the first time may lead to
 	 * the removal of the FS_MODIFY bit in calculated mask if it was set
-	 * because of an ignored mask that is now going to survive FS_MODIFY.
+	 * because of an ignore mask that is now going to survive FS_MODIFY.
 	 */
 	if ((fan_flags & FAN_MARK_IGNORED_MASK) &&
 	    (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
@@ -1123,7 +1123,7 @@ static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 	if (!(fan_flags & FAN_MARK_IGNORED_MASK))
 		fsn_mark->mask |= mask;
 	else
-		fsn_mark->ignored_mask |= mask;
+		fsn_mark->ignore_mask |= mask;
 
 	recalc = fsnotify_calc_mask(fsn_mark) &
 		~fsnotify_conn_mask(fsn_mark->connector);
@@ -1261,7 +1261,7 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group,
 
 	/*
 	 * If some other task has this inode open for write we should not add
-	 * an ignored mark, unless that ignored mark is supposed to survive
+	 * an ignore mask, unless that ignore mask is supposed to survive
 	 * modification changes anyway.
 	 */
 	if ((flags & FAN_MARK_IGNORED_MASK) &&
@@ -1557,7 +1557,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	__kernel_fsid_t __fsid, *fsid = NULL;
 	u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
 	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
-	bool ignored = flags & FAN_MARK_IGNORED_MASK;
+	bool ignore = flags & FAN_MARK_IGNORED_MASK;
 	unsigned int obj_type, fid_mode;
 	u32 umask = 0;
 	int ret;
@@ -1606,8 +1606,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	if (mask & ~valid_mask)
 		return -EINVAL;
 
-	/* Event flags (ONDIR, ON_CHILD) are meaningless in ignored mask */
-	if (ignored)
+	/*
+	 * Event flags (FAN_ONDIR, FAN_EVENT_ON_CHILD) have no effect with
+	 * FAN_MARK_IGNORED_MASK.
+	 */
+	if (ignore)
 		mask &= ~FANOTIFY_EVENT_FLAGS;
 
 	f = fdget(fanotify_fd);
@@ -1721,7 +1724,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 		 * events with parent/name info for non-directory.
 		 */
 		if ((fid_mode & FAN_REPORT_DIR_FID) &&
-		    (flags & FAN_MARK_ADD) && !ignored)
+		    (flags & FAN_MARK_ADD) && !ignore)
 			mask |= FAN_EVENT_ON_CHILD;
 	}
 
diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
index 59fb40abe33d..55081ae3a6ec 100644
--- a/fs/notify/fdinfo.c
+++ b/fs/notify/fdinfo.c
@@ -113,7 +113,7 @@ static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark)
 			return;
 		seq_printf(m, "fanotify ino:%lx sdev:%x mflags:%x mask:%x ignored_mask:%x ",
 			   inode->i_ino, inode->i_sb->s_dev,
-			   mflags, mark->mask, mark->ignored_mask);
+			   mflags, mark->mask, mark->ignore_mask);
 		show_mark_fhandle(m, inode);
 		seq_putc(m, '\n');
 		iput(inode);
@@ -121,12 +121,12 @@ static void fanotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark)
 		struct mount *mnt = fsnotify_conn_mount(mark->connector);
 
 		seq_printf(m, "fanotify mnt_id:%x mflags:%x mask:%x ignored_mask:%x\n",
-			   mnt->mnt_id, mflags, mark->mask, mark->ignored_mask);
+			   mnt->mnt_id, mflags, mark->mask, mark->ignore_mask);
 	} else if (mark->connector->type == FSNOTIFY_OBJ_TYPE_SB) {
 		struct super_block *sb = fsnotify_conn_sb(mark->connector);
 
 		seq_printf(m, "fanotify sdev:%x mflags:%x mask:%x ignored_mask:%x\n",
-			   sb->s_dev, mflags, mark->mask, mark->ignored_mask);
+			   sb->s_dev, mflags, mark->mask, mark->ignore_mask);
 	}
 }
 
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 0b3e74935cb4..8687562df2e3 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -324,7 +324,8 @@ static int send_to_group(__u32 mask, const void *data, int data_type,
 	struct fsnotify_group *group = NULL;
 	__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
 	__u32 marks_mask = 0;
-	__u32 marks_ignored_mask = 0;
+	__u32 marks_ignore_mask = 0;
+	bool is_dir = mask & FS_ISDIR;
 	struct fsnotify_mark *mark;
 	int type;
 
@@ -336,7 +337,7 @@ static int send_to_group(__u32 mask, const void *data, int data_type,
 		fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
 			if (!(mark->flags &
 			      FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
-				mark->ignored_mask = 0;
+				mark->ignore_mask = 0;
 		}
 	}
 
@@ -344,14 +345,15 @@ static int send_to_group(__u32 mask, const void *data, int data_type,
 	fsnotify_foreach_iter_mark_type(iter_info, mark, type) {
 		group = mark->group;
 		marks_mask |= mark->mask;
-		marks_ignored_mask |= mark->ignored_mask;
+		marks_ignore_mask |=
+			fsnotify_effective_ignore_mask(mark, is_dir, type);
 	}
 
-	pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignored_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
-		 __func__, group, mask, marks_mask, marks_ignored_mask,
+	pr_debug("%s: group=%p mask=%x marks_mask=%x marks_ignore_mask=%x data=%p data_type=%d dir=%p cookie=%d\n",
+		 __func__, group, mask, marks_mask, marks_ignore_mask,
 		 data, data_type, dir, cookie);
 
-	if (!(test_mask & marks_mask & ~marks_ignored_mask))
+	if (!(test_mask & marks_mask & ~marks_ignore_mask))
 		return 0;
 
 	if (group->ops->handle_event) {
@@ -423,7 +425,8 @@ static bool fsnotify_iter_select_report_types(
 			 * But is *this mark* watching children?
 			 */
 			if (type == FSNOTIFY_ITER_TYPE_PARENT &&
-			    !(mark->mask & FS_EVENT_ON_CHILD))
+			    !(mark->mask & FS_EVENT_ON_CHILD) &&
+			    !(fsnotify_ignore_mask(mark) & FS_EVENT_ON_CHILD))
 				continue;
 
 			fsnotify_iter_set_report_type(iter_info, type);
@@ -532,8 +535,8 @@ int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
 
 
 	/*
-	 * If this is a modify event we may need to clear some ignored masks.
-	 * In that case, the object with ignored masks will have the FS_MODIFY
+	 * If this is a modify event we may need to clear some ignore masks.
+	 * In that case, the object with ignore masks will have the FS_MODIFY
 	 * event in its mask.
 	 * Otherwise, return if none of the marks care about this type of event.
 	 */
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 9560734759fa..a7d605d49a84 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -518,8 +518,8 @@ struct fsnotify_mark {
 	struct hlist_node obj_list;
 	/* Head of list of marks for an object [mark ref] */
 	struct fsnotify_mark_connector *connector;
-	/* Events types to ignore [mark->lock, group->mark_mutex] */
-	__u32 ignored_mask;
+	/* Events types and flags to ignore [mark->lock, group->mark_mutex] */
+	__u32 ignore_mask;
 	/* General fsnotify mark flags */
 #define FSNOTIFY_MARK_FLAG_ALIVE		0x0001
 #define FSNOTIFY_MARK_FLAG_ATTACHED		0x0002
@@ -529,6 +529,7 @@ struct fsnotify_mark {
 	/* fanotify mark flags */
 #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY	0x0100
 #define FSNOTIFY_MARK_FLAG_NO_IREF		0x0200
+#define FSNOTIFY_MARK_FLAG_IGNORE_FLAGS		0x0400
 	unsigned int flags;		/* flags [mark->lock] */
 };
 
@@ -655,15 +656,91 @@ extern void fsnotify_remove_queued_event(struct fsnotify_group *group,
 
 /* functions used to manipulate the marks attached to inodes */
 
-/* Get mask for calculating object interest taking ignored mask into account */
+/*
+ * Canonical "ignore mask" including event flags.
+ *
+ * Note the subtle semantic difference from the legacy ->ignored_mask.
+ * ->ignored_mask traditionally only meant which events should be ignored,
+ * while ->ignore_mask also includes flags regarding the type of objects on
+ * which events should be ignored.
+ */
+static inline __u32 fsnotify_ignore_mask(struct fsnotify_mark *mark)
+{
+	__u32 ignore_mask = mark->ignore_mask;
+
+	/* The event flags in ignore mask take effect */
+	if (mark->flags & FSNOTIFY_MARK_FLAG_IGNORE_FLAGS)
+		return ignore_mask;
+
+	/*
+	 * Legacy behavior:
+	 * - Always ignore events on dir
+	 * - Ignore events on child if parent is watching children
+	 */
+	ignore_mask |= FS_ISDIR;
+	ignore_mask &= ~FS_EVENT_ON_CHILD;
+	ignore_mask |= mark->mask & FS_EVENT_ON_CHILD;
+
+	return ignore_mask;
+}
+
+/* Legacy ignored_mask - only event types to ignore */
+static inline __u32 fsnotify_ignored_events(struct fsnotify_mark *mark)
+{
+	return mark->ignore_mask & ALL_FSNOTIFY_EVENTS;
+}
+
+/*
+ * Check if mask (or ignore mask) should be applied depending if victim is a
+ * directory and whether it is reported to a watching parent.
+ */
+static inline bool fsnotify_mask_applicable(__u32 mask, bool is_dir,
+					    int iter_type)
+{
+	/* Should mask be applied to a directory? */
+	if (is_dir && !(mask & FS_ISDIR))
+		return false;
+
+	/* Should mask be applied to a child? */
+	if (iter_type == FSNOTIFY_ITER_TYPE_PARENT &&
+	    !(mask & FS_EVENT_ON_CHILD))
+		return false;
+
+	return true;
+}
+
+/*
+ * Effective ignore mask taking into account if event victim is a
+ * directory and whether it is reported to a watching parent.
+ */
+static inline __u32 fsnotify_effective_ignore_mask(struct fsnotify_mark *mark,
+						   bool is_dir, int iter_type)
+{
+	__u32 ignore_mask = fsnotify_ignored_events(mark);
+
+	if (!ignore_mask)
+		return 0;
+
+	/* For non-dir and non-child, no need to consult the event flags */
+	if (!is_dir && iter_type != FSNOTIFY_ITER_TYPE_PARENT)
+		return ignore_mask;
+
+	ignore_mask = fsnotify_ignore_mask(mark);
+	if (!fsnotify_mask_applicable(ignore_mask, is_dir, iter_type))
+		return 0;
+
+	return ignore_mask & ALL_FSNOTIFY_EVENTS;
+}
+
+/* Get mask for calculating object interest taking ignore mask into account */
 static inline __u32 fsnotify_calc_mask(struct fsnotify_mark *mark)
 {
 	__u32 mask = mark->mask;
 
-	if (!mark->ignored_mask)
+	if (!fsnotify_ignored_events(mark))
 		return mask;
 
-	/* Interest in FS_MODIFY may be needed for clearing ignored mask */
+	/* Interest in FS_MODIFY may be needed for clearing ignore mask */
 	if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 		mask |= FS_MODIFY;
 
@@ -671,7 +748,7 @@ static inline __u32 fsnotify_calc_mask(struct fsnotify_mark *mark)
 	 * If mark is interested in ignoring events on children, the object must
 	 * show interest in those events for fsnotify_parent() to notice it.
 	 */
-	return mask | (mark->ignored_mask & ALL_FSNOTIFY_EVENTS);
+	return mask | mark->ignore_mask;
 }
 
 /* Get mask of events for a list of marks */
-- 
2.25.1

[PATCH v3 2/3] fanotify: cleanups for fanotify_mark() input validations

[Amir Goldstein]

Create helper fanotify_may_update_existing_mark() for checking for
conflicts between existing mark flags and fanotify_mark() flags.

Use variable mark_cmd to make the checks for mark command bits
cleaner.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify_user.c | 30 +++++++++++++++++++++---------
 include/linux/fanotify.h           |  9 +++++----
 2 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index a9eea037fee9..6781d46cd37c 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1187,6 +1187,19 @@ static int fanotify_group_init_error_pool(struct fsnotify_group *group)
 					 sizeof(struct fanotify_error_event));
 }
 
+static int fanotify_may_update_existing_mark(struct fsnotify_mark *fsn_mark,
+					      unsigned int fan_flags)
+{
+	/*
+	 * Non evictable mark cannot be downgraded to evictable mark.
+	 */
+	if (fan_flags & FAN_MARK_EVICTABLE &&
+	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
+		return -EEXIST;
+
+	return 0;
+}
+
 static int fanotify_add_mark(struct fsnotify_group *group,
 			     fsnotify_connp_t *connp, unsigned int obj_type,
 			     __u32 mask, unsigned int fan_flags,
@@ -1208,13 +1221,11 @@ static int fanotify_add_mark(struct fsnotify_group *group,
 	}
 
 	/*
-	 * Non evictable mark cannot be downgraded to evictable mark.
+	 * Check if requested mark flags conflict with an existing mark flags.
 	 */
-	if (fan_flags & FAN_MARK_EVICTABLE &&
-	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF)) {
-		ret = -EEXIST;
+	ret = fanotify_may_update_existing_mark(fsn_mark, fan_flags);
+	if (ret)
 		goto out;
-	}
 
 	/*
 	 * Error events are pre-allocated per group, only if strictly
@@ -1557,6 +1568,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	__kernel_fsid_t __fsid, *fsid = NULL;
 	u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
 	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
+	unsigned int mark_cmd = flags & FANOTIFY_MARK_CMD_BITS;
 	bool ignore = flags & FAN_MARK_IGNORED_MASK;
 	unsigned int obj_type, fid_mode;
 	u32 umask = 0;
@@ -1586,7 +1598,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 		return -EINVAL;
 	}
 
-	switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
+	switch (mark_cmd) {
 	case FAN_MARK_ADD:
 	case FAN_MARK_REMOVE:
 		if (!mask)
@@ -1675,7 +1687,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	if (mask & FAN_RENAME && !(fid_mode & FAN_REPORT_NAME))
 		goto fput_and_out;
 
-	if (flags & FAN_MARK_FLUSH) {
+	if (mark_cmd == FAN_MARK_FLUSH) {
 		ret = 0;
 		if (mark_type == FAN_MARK_MOUNT)
 			fsnotify_clear_vfsmount_marks_by_group(group);
@@ -1691,7 +1703,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	if (ret)
 		goto fput_and_out;
 
-	if (flags & FAN_MARK_ADD) {
+	if (mark_cmd == FAN_MARK_ADD) {
 		ret = fanotify_events_supported(group, &path, mask, flags);
 		if (ret)
 			goto path_put_and_out;
@@ -1729,7 +1741,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	}
 
 	/* create/update an inode mark */
-	switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) {
+	switch (mark_cmd) {
 	case FAN_MARK_ADD:
 		if (mark_type == FAN_MARK_MOUNT)
 			ret = fanotify_add_vfsmount_mark(group, mnt, mask,
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index e517dbcf74ed..a7207f092fd1 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -59,15 +59,16 @@
 #define FANOTIFY_MARK_TYPE_BITS	(FAN_MARK_INODE | FAN_MARK_MOUNT | \
 				 FAN_MARK_FILESYSTEM)
 
+#define FANOTIFY_MARK_CMD_BITS	(FAN_MARK_ADD | FAN_MARK_REMOVE | \
+				 FAN_MARK_FLUSH)
+
 #define FANOTIFY_MARK_FLAGS	(FANOTIFY_MARK_TYPE_BITS | \
-				 FAN_MARK_ADD | \
-				 FAN_MARK_REMOVE | \
+				 FANOTIFY_MARK_CMD_BITS | \
 				 FAN_MARK_DONT_FOLLOW | \
 				 FAN_MARK_ONLYDIR | \
 				 FAN_MARK_IGNORED_MASK | \
 				 FAN_MARK_IGNORED_SURV_MODIFY | \
-				 FAN_MARK_EVICTABLE | \
-				 FAN_MARK_FLUSH)
+				 FAN_MARK_EVICTABLE)
 
 /*
  * Events that can be reported with data type FSNOTIFY_EVENT_PATH.
-- 
2.25.1

[PATCH v3 3/3] fanotify: introduce FAN_MARK_IGNORE

[Amir Goldstein]

This flag is a new way to configure ignore mask which allows adding and
removing the event flags FAN_ONDIR and FAN_EVENT_ON_CHILD in ignore mask.

The legacy FAN_MARK_IGNORED_MASK flag would always ignore events on
directories and would ignore events on children depending on whether
the FAN_EVENT_ON_CHILD flag was set in the (non ignored) mask.

FAN_MARK_IGNORE can be used to ignore events on children without setting
FAN_EVENT_ON_CHILD in the mark's mask and will not ignore events on
directories unconditionally, only when FAN_ONDIR is set in ignore mask.

The new behavior is non-downgradable.  After calling fanotify_mark() with
FAN_MARK_IGNORE once, calling fanotify_mark() with FAN_MARK_IGNORED_MASK
on the same object will return EEXIST error.

Setting the event flags with FAN_MARK_IGNORE on a non-dir inode mark
has no meaning and will return ENOTDIR error.

The meaning of FAN_MARK_IGNORED_SURV_MODIFY is preserved with the new
FAN_MARK_IGNORE flag, but with a few semantic differences:

1. FAN_MARK_IGNORED_SURV_MODIFY is required for filesystem and mount
   marks and on an inode mark on a directory. Omitting this flag
   will return EINVAL or EISDIR error.

2. An ignore mask on a non-directory inode that survives modify could
   never be downgraded to an ignore mask that does not survive modify.
   With new FAN_MARK_IGNORE semantics we make that rule explicit -
   trying to update a surviving ignore mask without the flag
   FAN_MARK_IGNORED_SURV_MODIFY will return EEXIST error.

The conveniene macro FAN_MARK_IGNORE_SURV is added for
(FAN_MARK_IGNORE | FAN_MARK_IGNORED_SURV_MODIFY), because the
common case should use short constant names.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.h      |  2 +
 fs/notify/fanotify/fanotify_user.c | 63 +++++++++++++++++++++++++-----
 include/linux/fanotify.h           |  5 ++-
 include/uapi/linux/fanotify.h      |  8 ++++
 4 files changed, 67 insertions(+), 11 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index 80e0ec95b113..c54d0b404373 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -499,6 +499,8 @@ static inline unsigned int fanotify_mark_user_flags(struct fsnotify_mark *mark)
 		mflags |= FAN_MARK_IGNORED_SURV_MODIFY;
 	if (mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF)
 		mflags |= FAN_MARK_EVICTABLE;
+	if (mark->flags & FSNOTIFY_MARK_FLAG_IGNORE_FLAGS)
+		mflags |= FAN_MARK_IGNORE;
 
 	return mflags;
 }
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 6781d46cd37c..006be1ca048a 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1009,7 +1009,7 @@ static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
 	mask &= ~umask;
 	spin_lock(&fsn_mark->lock);
 	oldmask = fsnotify_calc_mask(fsn_mark);
-	if (!(flags & FAN_MARK_IGNORED_MASK)) {
+	if (!(flags & FANOTIFY_MARK_IGNORE_BITS)) {
 		fsn_mark->mask &= ~mask;
 	} else {
 		fsn_mark->ignore_mask &= ~mask;
@@ -1085,15 +1085,24 @@ static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
 				       unsigned int fan_flags)
 {
 	bool want_iref = !(fan_flags & FAN_MARK_EVICTABLE);
+	unsigned int ignore = fan_flags & FANOTIFY_MARK_IGNORE_BITS;
 	bool recalc = false;
 
+	/*
+	 * When using FAN_MARK_IGNORE for the first time, mark starts using
+	 * independent event flags in ignore mask.  After that, trying to
+	 * update the ignore mask with the old FAN_MARK_IGNORED_MASK API
+	 * will result in EEXIST error.
+	 */
+	if (ignore == FAN_MARK_IGNORE)
+		fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORE_FLAGS;
+
 	/*
 	 * Setting FAN_MARK_IGNORED_SURV_MODIFY for the first time may lead to
 	 * the removal of the FS_MODIFY bit in calculated mask if it was set
 	 * because of an ignore mask that is now going to survive FS_MODIFY.
 	 */
-	if ((fan_flags & FAN_MARK_IGNORED_MASK) &&
-	    (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
+	if (ignore && (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) {
 		fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 		if (!(fsn_mark->mask & FS_MODIFY))
@@ -1120,7 +1129,7 @@ static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 	bool recalc;
 
 	spin_lock(&fsn_mark->lock);
-	if (!(fan_flags & FAN_MARK_IGNORED_MASK))
+	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
 		fsn_mark->mask |= mask;
 	else
 		fsn_mark->ignore_mask |= mask;
@@ -1197,6 +1206,24 @@ static int fanotify_may_update_existing_mark(struct fsnotify_mark *fsn_mark,
 	    !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
 		return -EEXIST;
 
+	/*
+	 * New ignore mask semantics cannot be downgraded to old semantics.
+	 */
+	if (fan_flags & FAN_MARK_IGNORED_MASK &&
+	    fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORE_FLAGS)
+		return -EEXIST;
+
+	/*
+	 * An ignore mask that survives modify could never be downgraded to not
+	 * survive modify.  With new FAN_MARK_IGNORE semantics we make that rule
+	 * explicit and return an error when trying to update the ignore mask
+	 * without the original FAN_MARK_IGNORED_SURV_MODIFY value.
+	 */
+	if (fan_flags & FAN_MARK_IGNORE &&
+	    !(fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
+	    fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)
+		return -EEXIST;
+
 	return 0;
 }
 
@@ -1231,7 +1258,8 @@ static int fanotify_add_mark(struct fsnotify_group *group,
 	 * Error events are pre-allocated per group, only if strictly
 	 * needed (i.e. FAN_FS_ERROR was requested).
 	 */
-	if (!(fan_flags & FAN_MARK_IGNORED_MASK) && (mask & FAN_FS_ERROR)) {
+	if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS) &&
+	    (mask & FAN_FS_ERROR)) {
 		ret = fanotify_group_init_error_pool(group);
 		if (ret)
 			goto out;
@@ -1275,7 +1303,7 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group,
 	 * an ignore mask, unless that ignore mask is supposed to survive
 	 * modification changes anyway.
 	 */
-	if ((flags & FAN_MARK_IGNORED_MASK) &&
+	if ((flags & FANOTIFY_MARK_IGNORE_BITS) &&
 	    !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
 	    inode_is_open_for_write(inode))
 		return 0;
@@ -1531,7 +1559,8 @@ static int fanotify_events_supported(struct fsnotify_group *group,
 	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
 	/* Strict validation of events in non-dir inode mask with v5.17+ APIs */
 	bool strict_dir_events = FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID) ||
-				 (mask & FAN_RENAME);
+				 (mask & FAN_RENAME) ||
+				 (flags & FAN_MARK_IGNORE);
 
 	/*
 	 * Some filesystems such as 'proc' acquire unusual locks when opening
@@ -1569,7 +1598,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
 	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
 	unsigned int mark_cmd = flags & FANOTIFY_MARK_CMD_BITS;
-	bool ignore = flags & FAN_MARK_IGNORED_MASK;
+	unsigned int ignore = flags & FANOTIFY_MARK_IGNORE_BITS;
 	unsigned int obj_type, fid_mode;
 	u32 umask = 0;
 	int ret;
@@ -1618,12 +1647,19 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	if (mask & ~valid_mask)
 		return -EINVAL;
 
+
+	/* We don't allow FAN_MARK_IGNORE & FAN_MARK_IGNORED_MASK together */
+	if (ignore == (FAN_MARK_IGNORE | FAN_MARK_IGNORED_MASK))
+		return -EINVAL;
+
 	/*
 	 * Event flags (FAN_ONDIR, FAN_EVENT_ON_CHILD) have no effect with
 	 * FAN_MARK_IGNORED_MASK.
 	 */
-	if (ignore)
+	if (ignore == FAN_MARK_IGNORED_MASK) {
 		mask &= ~FANOTIFY_EVENT_FLAGS;
+		umask = FANOTIFY_EVENT_FLAGS;
+	}
 
 	f = fdget(fanotify_fd);
 	if (unlikely(!f.file))
@@ -1727,6 +1763,13 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	else
 		mnt = path.mnt;
 
+	ret = mnt ? -EINVAL : -EISDIR;
+	/* FAN_MARK_IGNORE requires SURV_MODIFY for sb/mount/dir marks */
+	if (mark_cmd == FAN_MARK_ADD && ignore == FAN_MARK_IGNORE &&
+	    (mnt || S_ISDIR(inode->i_mode)) &&
+	    !(flags & FAN_MARK_IGNORED_SURV_MODIFY))
+		goto path_put_and_out;
+
 	/* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */
 	if (mnt || !S_ISDIR(inode->i_mode)) {
 		mask &= ~FAN_EVENT_ON_CHILD;
@@ -1819,7 +1862,7 @@ static int __init fanotify_user_setup(void)
 
 	BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
 	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 12);
-	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 10);
+	BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 11);
 
 	fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
 					 SLAB_PANIC|SLAB_ACCOUNT);
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index a7207f092fd1..8ad743def6f3 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -62,11 +62,14 @@
 #define FANOTIFY_MARK_CMD_BITS	(FAN_MARK_ADD | FAN_MARK_REMOVE | \
 				 FAN_MARK_FLUSH)
 
+#define FANOTIFY_MARK_IGNORE_BITS (FAN_MARK_IGNORED_MASK | \
+				   FAN_MARK_IGNORE)
+
 #define FANOTIFY_MARK_FLAGS	(FANOTIFY_MARK_TYPE_BITS | \
 				 FANOTIFY_MARK_CMD_BITS | \
+				 FANOTIFY_MARK_IGNORE_BITS | \
 				 FAN_MARK_DONT_FOLLOW | \
 				 FAN_MARK_ONLYDIR | \
-				 FAN_MARK_IGNORED_MASK | \
 				 FAN_MARK_IGNORED_SURV_MODIFY | \
 				 FAN_MARK_EVICTABLE)
 
diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
index f1f89132d60e..d8536d77fea1 100644
--- a/include/uapi/linux/fanotify.h
+++ b/include/uapi/linux/fanotify.h
@@ -83,12 +83,20 @@
 #define FAN_MARK_FLUSH		0x00000080
 /* FAN_MARK_FILESYSTEM is	0x00000100 */
 #define FAN_MARK_EVICTABLE	0x00000200
+/* This bit is mutually exclusive with FAN_MARK_IGNORED_MASK bit */
+#define FAN_MARK_IGNORE		0x00000400
 
 /* These are NOT bitwise flags.  Both bits can be used togther.  */
 #define FAN_MARK_INODE		0x00000000
 #define FAN_MARK_MOUNT		0x00000010
 #define FAN_MARK_FILESYSTEM	0x00000100
 
+/*
+ * Convenience macro - FAN_MARK_IGNORE requires FAN_MARK_IGNORED_SURV_MODIFY
+ * for non-inode mark types.
+ */
+#define FAN_MARK_IGNORE_SURV	(FAN_MARK_IGNORE | FAN_MARK_IGNORED_SURV_MODIFY)
+
 /* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_MARK_FLAGS	(FAN_MARK_ADD |\
 				 FAN_MARK_REMOVE |\
-- 
2.25.1

Re: [PATCH v3 1/3] fanotify: prepare for setting event flags in ignore mask

[Jan Kara]

On Wed 29-06-22 17:42:08, Amir Goldstein wrote:
> @@ -529,6 +529,7 @@ struct fsnotify_mark {
>  	/* fanotify mark flags */
>  #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY	0x0100
>  #define FSNOTIFY_MARK_FLAG_NO_IREF		0x0200
> +#define FSNOTIFY_MARK_FLAG_IGNORE_FLAGS		0x0400
>  	unsigned int flags;		/* flags [mark->lock] */
>  };

The whole series looks good to me so I'll test it and queue it up. Just I
find the name FSNOTIFY_MARK_FLAG_IGNORE_FLAGS somewhat confusing because I
had to think whether it means "mark should ignore flags" or whether it
means "ignore mark has flags". So I'll rename this flag to
FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS on commit.

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH v3 1/3] fanotify: prepare for setting event flags in ignore mask

[Amir Goldstein]

On Fri, Jul 1, 2022 at 3:47 PM Jan Kara <jack@suse.cz> wrote:
>
> On Wed 29-06-22 17:42:08, Amir Goldstein wrote:
> > @@ -529,6 +529,7 @@ struct fsnotify_mark {
> >       /* fanotify mark flags */
> >  #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY       0x0100
> >  #define FSNOTIFY_MARK_FLAG_NO_IREF           0x0200
> > +#define FSNOTIFY_MARK_FLAG_IGNORE_FLAGS              0x0400
> >       unsigned int flags;             /* flags [mark->lock] */
> >  };
>
> The whole series looks good to me so I'll test it and queue it up. Just I
> find the name FSNOTIFY_MARK_FLAG_IGNORE_FLAGS somewhat confusing because I
> had to think whether it means "mark should ignore flags" or whether it
> means "ignore mark has flags". So I'll rename this flag to
> FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS on commit.

Excellent.
Thanks!

Amir.