[for-linus][PATCH 0/8] tracefs/eventfs: Fixes and cleanups for v6.10

[for-linus][PATCH 0/8] tracefs/eventfs: Fixes and cleanups for v6.10

[Steven Rostedt]

tracefs/eventfs fixes and updates for v6.10:

Bug fixes:

- The eventfs directories need to have unique inode numbers. Make sure that
  they do not get the default file inode number.

- Update the inode uid and gid fields on remount.
  When a remount happens where a uid and/or gid is specified, all the tracefs
  files and directories should get the specified uid and/or gid. But this
  can be sporadic when some uids were assigned already. There's already
  a list of inodes that are allocated. Just update their uid and gid fields
  at the time of remount.

- Update the eventfs_inodes on remount from the top level "events" descriptor.
  There was a bug where not all the eventfs files or directories where
  getting updated on remount. One fix was to clear the SAVED_UID/GID
  flags from the inode list during the iteration of the inodes during
  the remount. But because the eventfs inodes can be freed when the last
  referenced is released, not all the eventfs_inodes were being updated.
  This lead to the ownership selftest to fail if it was run a second
  time (the first time would leave eventfs_inodes with no corresponding
  tracefs_inode).

  Instead, for eventfs_inodes, only process the "events" eventfs_inode
  from the list iteration, as it is guaranteed to have a tracefs_inode
  (it's never freed while the "events" directory exists). As it has
  a list of its children, and the children have a list of their children,
  just iterate all the eventfs_inodes from the "events" descriptor and
  it is guaranteed to get all of them.

- Clear the EVENT_INODE flag from the tracefs_drop_inode() callback.
  Currently the EVENTFS_INODE FLAG is cleared in the tracefs_d_iput()
  callback. But this is the wrong location. The iput() callback is
  called when the last reference to the dentry inode is hit. There could
  be a case where two dentry's have the same inode, and the flag will
  be cleared prematurely. The flag needs to be cleared when the last
  reference of the inode is dropped and that happens in the inode's
  drop_inode() callback handler.

Clean ups:

- Consolidate the creation of a tracefs_inode for an eventfs_inode
  A tracefs_inode is created for both files and directories of the
  eventfs system. It is open coded. Instead, consolidate it into a
  single eventfs_get_inode() function call.

- Remove the eventfs getattr and permission callbacks.
  The permissions for the eventfs files and directories are updated
  when the inodes are created, on remount, and when the user sets
  them (via setattr). The inodes hold the current permissions so
  there is no need to have custom getattr or permissions callbacks
  as they will more likely cause them to be incorrect. The inode's
  permissions are updated when they should be updated. Remove the
  getattr and permissions inode callbacks.

- Do not update eventfs_inode attributes on creation of inodes.
  The eventfs_inodes attribute field is used to store the permissions
  of the directories and files for when their corresponding inodes
  are freed and are created again. But when the creation of the inodes
  happen, the eventfs_inode attributes are recalculated. The
  recalculation should only happen when the permissions change for
  a given file or directory. Currently, the attribute changes are
  just being set to their current files so this is not a bug, but
  it's unnecessary and error prone. Stop doing that.

- The events directory inode is created once when the events directory
  is created and deleted when it is deleted. It is now updated on
  remount and when the user changes the permissions. There's no need
  to use the eventfs_inode of the events directory to store the
  events directory permissions. But using it to store the default
  permissions for the files within the directory that have not been
  updated by the user can simplify the code.

  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
eventfs/urgent

Head SHA1: 2dd00ac1d38afba1b59e439abc300a9b0ce696bf


Steven Rostedt (Google) (8):
      eventfs: Keep the directories from having the same inode number as files
      tracefs: Update inode permissions on remount
      eventfs: Update all the eventfs_inodes from the events descriptor
      tracefs: Clear EVENT_INODE flag in tracefs_drop_inode()
      eventfs: Consolidate the eventfs_inode update in eventfs_get_inode()
      eventfs: Remove getattr and permission callbacks
      eventfs: Cleanup permissions in creation of inodes
      eventfs: Do not use attributes for events directory

----
 fs/tracefs/event_inode.c | 223 ++++++++++++++++++-----------------------------
 fs/tracefs/inode.c       |  48 ++++++----
 2 files changed, 116 insertions(+), 155 deletions(-)

[for-linus][PATCH 1/8] eventfs: Keep the directories from having the same inode number as files

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The directories require unique inode numbers but all the eventfs files
have the same inode number. Prevent the directories from having the same
inode numbers as the files as that can confuse some tooling.

Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.428826685@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Fixes: 834bf76add3e6 ("eventfs: Save directory inodes in the eventfs_inode structure")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 0256afdd4acf..55a40a730b10 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -50,8 +50,12 @@ static struct eventfs_root_inode *get_root_inode(struct eventfs_inode *ei)
 /* Just try to make something consistent and unique */
 static int eventfs_dir_ino(struct eventfs_inode *ei)
 {
-	if (!ei->ino)
+	if (!ei->ino) {
 		ei->ino = get_next_ino();
+		/* Must not have the file inode number */
+		if (ei->ino == EVENTFS_FILE_INODE_INO)
+			ei->ino = get_next_ino();
+	}
 
 	return ei->ino;
 }
-- 
2.43.0

[for-linus][PATCH 2/8] tracefs: Update inode permissions on remount

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

When a remount happens, if a gid or uid is specified update the inodes to
have the same gid and uid. This will allow the simplification of the
permissions logic for the dynamically created files and directories.

Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.592429986@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 17 +++++++++++++----
 fs/tracefs/inode.c       | 15 ++++++++++++---
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 55a40a730b10..5dfb1ccd56ea 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -317,20 +317,29 @@ void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
 	if (!ei)
 		return;
 
-	if (update_uid)
+	if (update_uid) {
 		ei->attr.mode &= ~EVENTFS_SAVE_UID;
+		ei->attr.uid = ti->vfs_inode.i_uid;
+	}
+
 
-	if (update_gid)
+	if (update_gid) {
 		ei->attr.mode &= ~EVENTFS_SAVE_GID;
+		ei->attr.gid = ti->vfs_inode.i_gid;
+	}
 
 	if (!ei->entry_attrs)
 		return;
 
 	for (int i = 0; i < ei->nr_entries; i++) {
-		if (update_uid)
+		if (update_uid) {
 			ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_UID;
-		if (update_gid)
+			ei->entry_attrs[i].uid = ti->vfs_inode.i_uid;
+		}
+		if (update_gid) {
 			ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_GID;
+			ei->entry_attrs[i].gid = ti->vfs_inode.i_gid;
+		}
 	}
 }
 
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index a827f6a716c4..9252e0d78ea2 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -373,12 +373,21 @@ static int tracefs_apply_options(struct super_block *sb, bool remount)
 
 		rcu_read_lock();
 		list_for_each_entry_rcu(ti, &tracefs_inodes, list) {
-			if (update_uid)
+			if (update_uid) {
 				ti->flags &= ~TRACEFS_UID_PERM_SET;
+				ti->vfs_inode.i_uid = fsi->uid;
+			}
 
-			if (update_gid)
+			if (update_gid) {
 				ti->flags &= ~TRACEFS_GID_PERM_SET;
-
+				ti->vfs_inode.i_gid = fsi->gid;
+			}
+
+			/*
+			 * Note, the above ti->vfs_inode updates are
+			 * used in eventfs_remount() so they must come
+			 * before calling it.
+			 */
 			if (ti->flags & TRACEFS_EVENT_INODE)
 				eventfs_remount(ti, update_uid, update_gid);
 		}
-- 
2.43.0

[for-linus][PATCH 3/8] eventfs: Update all the eventfs_inodes from the events descriptor

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The change to update the permissions of the eventfs_inode had the
misconception that using the tracefs_inode would find all the
eventfs_inodes that have been updated and reset them on remount.
The problem with this approach is that the eventfs_inodes are freed when
they are no longer used (basically the reason the eventfs system exists).
When they are freed, the updated eventfs_inodes are not reset on a remount
because their tracefs_inodes have been freed.

Instead, since the events directory eventfs_inode always has a
tracefs_inode pointing to it (it is not freed when finished), and the
events directory has a link to all its children, have the
eventfs_remount() function only operate on the events eventfs_inode and
have it descend into its children updating their uid and gids.

Link: https://lore.kernel.org/all/CAK7LNARXgaWw3kH9JgrnH4vK6fr8LDkNKf3wq8NhMWJrVwJyVQ@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.754424703@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options")
Reported-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 44 ++++++++++++++++++++++++++++------------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 5dfb1ccd56ea..129d0f54ba62 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -305,27 +305,27 @@ static const struct file_operations eventfs_file_operations = {
 	.llseek		= generic_file_llseek,
 };
 
-/*
- * On a remount of tracefs, if UID or GID options are set, then
- * the mount point inode permissions should be used.
- * Reset the saved permission flags appropriately.
- */
-void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
+static void eventfs_set_attrs(struct eventfs_inode *ei, bool update_uid, kuid_t uid,
+			      bool update_gid, kgid_t gid, int level)
 {
-	struct eventfs_inode *ei = ti->private;
+	struct eventfs_inode *ei_child;
 
-	if (!ei)
+	/* Update events/<system>/<event> */
+	if (WARN_ON_ONCE(level > 3))
 		return;
 
 	if (update_uid) {
 		ei->attr.mode &= ~EVENTFS_SAVE_UID;
-		ei->attr.uid = ti->vfs_inode.i_uid;
+		ei->attr.uid = uid;
 	}
 
-
 	if (update_gid) {
 		ei->attr.mode &= ~EVENTFS_SAVE_GID;
-		ei->attr.gid = ti->vfs_inode.i_gid;
+		ei->attr.gid = gid;
+	}
+
+	list_for_each_entry(ei_child, &ei->children, list) {
+		eventfs_set_attrs(ei_child, update_uid, uid, update_gid, gid, level + 1);
 	}
 
 	if (!ei->entry_attrs)
@@ -334,13 +334,31 @@ void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
 	for (int i = 0; i < ei->nr_entries; i++) {
 		if (update_uid) {
 			ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_UID;
-			ei->entry_attrs[i].uid = ti->vfs_inode.i_uid;
+			ei->entry_attrs[i].uid = uid;
 		}
 		if (update_gid) {
 			ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_GID;
-			ei->entry_attrs[i].gid = ti->vfs_inode.i_gid;
+			ei->entry_attrs[i].gid = gid;
 		}
 	}
+
+}
+
+/*
+ * On a remount of tracefs, if UID or GID options are set, then
+ * the mount point inode permissions should be used.
+ * Reset the saved permission flags appropriately.
+ */
+void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
+{
+	struct eventfs_inode *ei = ti->private;
+
+	/* Only the events directory does the updates */
+	if (!ei || !ei->is_events || ei->is_freed)
+		return;
+
+	eventfs_set_attrs(ei, update_uid, ti->vfs_inode.i_uid,
+			  update_gid, ti->vfs_inode.i_gid, 0);
 }
 
 /* Return the evenfs_inode of the "events" directory */
-- 
2.43.0

[for-linus][PATCH 4/8] tracefs: Clear EVENT_INODE flag in tracefs_drop_inode()

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

When the inode is being dropped from the dentry, the TRACEFS_EVENT_INODE
flag needs to be cleared to prevent a remount from calling
eventfs_remount() on the tracefs_inode private data. There's a race
between the inode is dropped (and the dentry freed) to where the inode is
actually freed. If a remount happens between the two, the eventfs_inode
could be accessed after it is freed (only the dentry keeps a ref count on
it).

Currently the TRACEFS_EVENT_INODE flag is cleared from the dentry iput()
function. But this is incorrect, as it is possible that the inode has
another reference to it. The flag should only be cleared when the inode is
really being dropped and has no more references. That happens in the
drop_inode callback of the inode, as that gets called when the last
reference of the inode is released.

Remove the tracefs_d_iput() function and move its logic to the more
appropriate tracefs_drop_inode() callback function.

Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.908205106@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/inode.c | 33 +++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 9252e0d78ea2..7c29f4afc23d 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -426,10 +426,26 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root)
 	return 0;
 }
 
+static int tracefs_drop_inode(struct inode *inode)
+{
+	struct tracefs_inode *ti = get_tracefs(inode);
+
+	/*
+	 * This inode is being freed and cannot be used for
+	 * eventfs. Clear the flag so that it doesn't call into
+	 * eventfs during the remount flag updates. The eventfs_inode
+	 * gets freed after an RCU cycle, so the content will still
+	 * be safe if the iteration is going on now.
+	 */
+	ti->flags &= ~TRACEFS_EVENT_INODE;
+
+	return 1;
+}
+
 static const struct super_operations tracefs_super_operations = {
 	.alloc_inode    = tracefs_alloc_inode,
 	.free_inode     = tracefs_free_inode,
-	.drop_inode     = generic_delete_inode,
+	.drop_inode     = tracefs_drop_inode,
 	.statfs		= simple_statfs,
 	.show_options	= tracefs_show_options,
 };
@@ -455,22 +471,7 @@ static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
 	return !(ei && ei->is_freed);
 }
 
-static void tracefs_d_iput(struct dentry *dentry, struct inode *inode)
-{
-	struct tracefs_inode *ti = get_tracefs(inode);
-
-	/*
-	 * This inode is being freed and cannot be used for
-	 * eventfs. Clear the flag so that it doesn't call into
-	 * eventfs during the remount flag updates. The eventfs_inode
-	 * gets freed after an RCU cycle, so the content will still
-	 * be safe if the iteration is going on now.
-	 */
-	ti->flags &= ~TRACEFS_EVENT_INODE;
-}
-
 static const struct dentry_operations tracefs_dentry_operations = {
-	.d_iput = tracefs_d_iput,
 	.d_revalidate = tracefs_d_revalidate,
 	.d_release = tracefs_d_release,
 };
-- 
2.43.0

[for-linus][PATCH 5/8] eventfs: Consolidate the eventfs_inode update in eventfs_get_inode()

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

To simplify the code, create a eventfs_get_inode() that is used when an
eventfs file or directory is created. Have the internal tracefs_inode
updated the appropriate flags in this function and update the inode's
mode as well.

Link: https://lore.kernel.org/lkml/20240522165031.624864160@goodmis.org

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 42 ++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 19 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 129d0f54ba62..92987b5c8d9d 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -412,6 +412,25 @@ static void update_inode_attr(struct dentry *dentry, struct inode *inode,
 		inode->i_gid = attr->gid;
 }
 
+static struct inode *eventfs_get_inode(struct dentry *dentry, struct eventfs_attr *attr,
+				       umode_t mode,  struct eventfs_inode *ei)
+{
+	struct tracefs_inode *ti;
+	struct inode *inode;
+
+	inode = tracefs_get_inode(dentry->d_sb);
+	if (!inode)
+		return NULL;
+
+	ti = get_tracefs(inode);
+	ti->private = ei;
+	ti->flags |= TRACEFS_EVENT_INODE;
+
+	update_inode_attr(dentry, inode, attr, mode);
+
+	return inode;
+}
+
 /**
  * lookup_file - look up a file in the tracefs filesystem
  * @parent_ei: Pointer to the eventfs_inode that represents parent of the file
@@ -432,7 +451,6 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
 				  void *data,
 				  const struct file_operations *fop)
 {
-	struct tracefs_inode *ti;
 	struct inode *inode;
 
 	if (!(mode & S_IFMT))
@@ -441,13 +459,11 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
 	if (WARN_ON_ONCE(!S_ISREG(mode)))
 		return ERR_PTR(-EIO);
 
-	inode = tracefs_get_inode(dentry->d_sb);
+	/* Only directories have ti->private set to an ei, not files */
+	inode = eventfs_get_inode(dentry, attr, mode, NULL);
 	if (unlikely(!inode))
 		return ERR_PTR(-ENOMEM);
 
-	/* If the user updated the directory's attributes, use them */
-	update_inode_attr(dentry, inode, attr, mode);
-
 	inode->i_op = &eventfs_file_inode_operations;
 	inode->i_fop = fop;
 	inode->i_private = data;
@@ -455,9 +471,6 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
 	/* All files will have the same inode number */
 	inode->i_ino = EVENTFS_FILE_INODE_INO;
 
-	ti = get_tracefs(inode);
-	ti->flags |= TRACEFS_EVENT_INODE;
-
 	// Files have their parent's ei as their fsdata
 	dentry->d_fsdata = get_ei(parent_ei);
 
@@ -477,28 +490,19 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
 static struct dentry *lookup_dir_entry(struct dentry *dentry,
 	struct eventfs_inode *pei, struct eventfs_inode *ei)
 {
-	struct tracefs_inode *ti;
 	struct inode *inode;
+	umode_t mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 
-	inode = tracefs_get_inode(dentry->d_sb);
+	inode = eventfs_get_inode(dentry, &ei->attr, mode, ei);
 	if (unlikely(!inode))
 		return ERR_PTR(-ENOMEM);
 
-	/* If the user updated the directory's attributes, use them */
-	update_inode_attr(dentry, inode, &ei->attr,
-			  S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO);
-
 	inode->i_op = &eventfs_dir_inode_operations;
 	inode->i_fop = &eventfs_file_operations;
 
 	/* All directories will have the same inode number */
 	inode->i_ino = eventfs_dir_ino(ei);
 
-	ti = get_tracefs(inode);
-	ti->flags |= TRACEFS_EVENT_INODE;
-	/* Only directories have ti->private set to an ei, not files */
-	ti->private = ei;
-
 	dentry->d_fsdata = get_ei(ei);
 
 	d_add(dentry, inode);
-- 
2.43.0

[for-linus][PATCH 6/8] eventfs: Remove getattr and permission callbacks

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Now that inodes have their permissions updated on remount, the only other
places to update the inode permissions are when they are created and in
the setattr callback. The getattr and permission callbacks are not needed
as the inodes should already be set at their proper settings.

Remove the callbacks, as it not only simplifies the code, but also allows
more flexibility to fix the inconsistencies with various corner cases
(like changing the permission of an instance directory).

Link: https://lore.kernel.org/lkml/20240522165031.782066021@goodmis.org

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 40 ----------------------------------------
 1 file changed, 40 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 92987b5c8d9d..f32c6f7eb29f 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -250,49 +250,9 @@ static void update_events_attr(struct eventfs_inode *ei, struct super_block *sb)
 		ei->attr.gid = parent->i_gid;
 }
 
-static void set_top_events_ownership(struct inode *inode)
-{
-	struct tracefs_inode *ti = get_tracefs(inode);
-	struct eventfs_inode *ei = ti->private;
-
-	/* The top events directory doesn't get automatically updated */
-	if (!ei || !ei->is_events)
-		return;
-
-	update_events_attr(ei, inode->i_sb);
-
-	if (!(ei->attr.mode & EVENTFS_SAVE_UID))
-		inode->i_uid = ei->attr.uid;
-
-	if (!(ei->attr.mode & EVENTFS_SAVE_GID))
-		inode->i_gid = ei->attr.gid;
-}
-
-static int eventfs_get_attr(struct mnt_idmap *idmap,
-			    const struct path *path, struct kstat *stat,
-			    u32 request_mask, unsigned int flags)
-{
-	struct dentry *dentry = path->dentry;
-	struct inode *inode = d_backing_inode(dentry);
-
-	set_top_events_ownership(inode);
-
-	generic_fillattr(idmap, request_mask, inode, stat);
-	return 0;
-}
-
-static int eventfs_permission(struct mnt_idmap *idmap,
-			      struct inode *inode, int mask)
-{
-	set_top_events_ownership(inode);
-	return generic_permission(idmap, inode, mask);
-}
-
 static const struct inode_operations eventfs_dir_inode_operations = {
 	.lookup		= eventfs_root_lookup,
 	.setattr	= eventfs_set_attr,
-	.getattr	= eventfs_get_attr,
-	.permission	= eventfs_permission,
 };
 
 static const struct inode_operations eventfs_file_inode_operations = {
-- 
2.43.0

[for-linus][PATCH 7/8] eventfs: Cleanup permissions in creation of inodes

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The permissions being set during the creation of the inodes was updating
eventfs_inode attributes as well. Those attributes should only be touched
by the setattr or remount operations, not during the creation of inodes.
The eventfs_inode attributes should only be used to set the inodes and
should not be modified during the inode creation.

Simplify the code and fix the situation by:

 1) Removing the eventfs_find_events() and doing a simple lookup for
    the events descriptor in eventfs_get_inode()

 2) Remove update_events_attr() as the attributes should only be used
    to update the inode and should not be modified here.

 3) Add update_inode_attr() that uses the attributes to determine what
    the inode permissions should be.

 4) As the parent_inode of the eventfs_root_inode structure is no longer
    needed, remove it.

Now on creation, the inode gets the proper permissions without causing
side effects to the ei->attr field.

Link: https://lore.kernel.org/lkml/20240522165031.944088388@goodmis.org

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 90 ++++++++++------------------------------
 1 file changed, 23 insertions(+), 67 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index f32c6f7eb29f..320e49056d3a 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -37,7 +37,6 @@ static DEFINE_MUTEX(eventfs_mutex);
 
 struct eventfs_root_inode {
 	struct eventfs_inode		ei;
-	struct inode			*parent_inode;
 	struct dentry			*events_dir;
 };
 
@@ -229,27 +228,6 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
 	return ret;
 }
 
-static void update_events_attr(struct eventfs_inode *ei, struct super_block *sb)
-{
-	struct eventfs_root_inode *rei;
-	struct inode *parent;
-
-	rei = get_root_inode(ei);
-
-	/* Use the parent inode permissions unless root set its permissions */
-	parent = rei->parent_inode;
-
-	if (rei->ei.attr.mode & EVENTFS_SAVE_UID)
-		ei->attr.uid = rei->ei.attr.uid;
-	else
-		ei->attr.uid = parent->i_uid;
-
-	if (rei->ei.attr.mode & EVENTFS_SAVE_GID)
-		ei->attr.gid = rei->ei.attr.gid;
-	else
-		ei->attr.gid = parent->i_gid;
-}
-
 static const struct inode_operations eventfs_dir_inode_operations = {
 	.lookup		= eventfs_root_lookup,
 	.setattr	= eventfs_set_attr,
@@ -321,60 +299,30 @@ void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
 			  update_gid, ti->vfs_inode.i_gid, 0);
 }
 
-/* Return the evenfs_inode of the "events" directory */
-static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)
+static void update_inode_attr(struct inode *inode, umode_t mode,
+			      struct eventfs_attr *attr, struct eventfs_root_inode *rei)
 {
-	struct eventfs_inode *ei;
-
-	do {
-		// The parent is stable because we do not do renames
-		dentry = dentry->d_parent;
-		// ... and directories always have d_fsdata
-		ei = dentry->d_fsdata;
-
-		/*
-		 * If the ei is being freed, the ownership of the children
-		 * doesn't matter.
-		 */
-		if (ei->is_freed)
-			return NULL;
-
-		// Walk upwards until you find the events inode
-	} while (!ei->is_events);
-
-	update_events_attr(ei, dentry->d_sb);
-
-	return ei;
-}
-
-static void update_inode_attr(struct dentry *dentry, struct inode *inode,
-			      struct eventfs_attr *attr, umode_t mode)
-{
-	struct eventfs_inode *events_ei = eventfs_find_events(dentry);
-
-	if (!events_ei)
-		return;
-
-	inode->i_mode = mode;
-	inode->i_uid = events_ei->attr.uid;
-	inode->i_gid = events_ei->attr.gid;
-
-	if (!attr)
-		return;
-
-	if (attr->mode & EVENTFS_SAVE_MODE)
+	if (attr && attr->mode & EVENTFS_SAVE_MODE)
 		inode->i_mode = attr->mode & EVENTFS_MODE_MASK;
+	else
+		inode->i_mode = mode;
 
-	if (attr->mode & EVENTFS_SAVE_UID)
+	if (attr && attr->mode & EVENTFS_SAVE_UID)
 		inode->i_uid = attr->uid;
+	else
+		inode->i_uid = rei->ei.attr.uid;
 
-	if (attr->mode & EVENTFS_SAVE_GID)
+	if (attr && attr->mode & EVENTFS_SAVE_GID)
 		inode->i_gid = attr->gid;
+	else
+		inode->i_gid = rei->ei.attr.gid;
 }
 
 static struct inode *eventfs_get_inode(struct dentry *dentry, struct eventfs_attr *attr,
 				       umode_t mode,  struct eventfs_inode *ei)
 {
+	struct eventfs_root_inode *rei;
+	struct eventfs_inode *pei;
 	struct tracefs_inode *ti;
 	struct inode *inode;
 
@@ -386,7 +334,16 @@ static struct inode *eventfs_get_inode(struct dentry *dentry, struct eventfs_att
 	ti->private = ei;
 	ti->flags |= TRACEFS_EVENT_INODE;
 
-	update_inode_attr(dentry, inode, attr, mode);
+	/* Find the top dentry that holds the "events" directory */
+	do {
+		dentry = dentry->d_parent;
+		/* Directories always have d_fsdata */
+		pei = dentry->d_fsdata;
+	} while (!pei->is_events);
+
+	rei = get_root_inode(pei);
+
+	update_inode_attr(inode, mode, attr, rei);
 
 	return inode;
 }
@@ -823,7 +780,6 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	// Note: we have a ref to the dentry from tracefs_start_creating()
 	rei = get_root_inode(ei);
 	rei->events_dir = dentry;
-	rei->parent_inode = d_inode(dentry->d_sb->s_root);
 
 	ei->entries = entries;
 	ei->nr_entries = size;
-- 
2.43.0

[for-linus][PATCH 8/8] eventfs: Do not use attributes for events directory

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The top "events" directory has a static inode (it's created when it is and
removed when the directory is removed). There's no need to use the events
ei->attr to determine its permissions. But it is used for saving the
permissions of the "events" directory for when it is created, as that is
needed for the default permissions for the files and directories
underneath it.

For example:

 # cd /sys/kernel/tracing
 # mkdir instances/foo
 # chown 1001 instances/foo/events

The files under instances/foo/events should still have the same owner as
instances/foo (which the instances/foo/events ei->attr will hold), but the
events directory now has owner 1001.

Link: https://lore.kernel.org/lkml/20240522165032.104981011@goodmis.org

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 320e49056d3a..5d88c184f0fc 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -210,7 +210,9 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
 	 * determined by the parent directory.
 	 */
 	if (dentry->d_inode->i_mode & S_IFDIR) {
-		update_attr(&ei->attr, iattr);
+		/* Just use the inode permissions for the events directory */
+		if (!ei->is_events)
+			update_attr(&ei->attr, iattr);
 
 	} else {
 		name = dentry->d_name.name;
@@ -789,14 +791,12 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	uid = d_inode(dentry->d_parent)->i_uid;
 	gid = d_inode(dentry->d_parent)->i_gid;
 
-	ei->attr.uid = uid;
-	ei->attr.gid = gid;
-
 	/*
-	 * When the "events" directory is created, it takes on the
-	 * permissions of its parent. But can be reset on remount.
+	 * The ei->attr will be used as the default values for the
+	 * files beneath this directory.
 	 */
-	ei->attr.mode |= EVENTFS_SAVE_UID | EVENTFS_SAVE_GID;
+	ei->attr.uid = uid;
+	ei->attr.gid = gid;
 
 	INIT_LIST_HEAD(&ei->children);
 	INIT_LIST_HEAD(&ei->list);
-- 
2.43.0