[for-linus][PATCH 0/9] tracing/tracefs: Fixes for v6.9

Steven Rostedt
2024-05-03T22:50:34Z

tracing and tracefs fixes for v6.9

- Minor fix for user_events interface
The ABI of creating a user event states that the fields
are separated by semicolons, and spaces should be ignored.
But the parsing expected at least one space to be there (which was incorrect).
Fix the reading of the string to handle fields separated by
semicolons but no space between them.

- Add test to user event selftests for no spaces between fields.

- Fix RCU callback of freeing an eventfs_inode.
The freeing of the eventfs_inode from the kref going to zero
freed the contents of the eventfs_inode and then used kfree_rcu()
to free the inode itself. But the contents should also be protected
by RCU. Switch to a call_rcu() that calls a function to free all
of the eventfs_inode after the RCU synchronization.

- The tracefs maps its own descriptor to a file represented by
eventfs. The freeing of this descriptor needs to know when the
last reference of an eventfs_inode is released, but currently
there is no interface for that. Add a "release" callback to
the eventfs_inode entry array that allows for freeing of data
that can be referenced by the eventfs_inode being opened.
Then increment the ref counter for this descriptor when the
eventfs_inode file is created, and decrement/free it when the
last reference to the eventfs_inode is released and the file
is removed.

- Fix the permission processing of eventfs.
The change to make the permissions of eventfs default to the mount
point but keep track of when changes were made had a side effect
that could cause security concerns. When the tracefs is remounted
with a given gid or uid, all the files within it should inherit
that gid or uid. But if the admin had changed the permission of
some file within the tracefs file system, it would not get updated
by the remount. This caused the kselftest of file permissions
to fail the second time it is run. The first time, all changes
would look fine, but the second time, because the changes were
"saved", the remount did not reset them.

Create a link list of all existing tracefs inodes, and clear the
saved flags on them on a remount if the remount changes the
corresponding gid or uid fields.

This also simplifies the code by removing the distinction between the
toplevel eventfs and an instance eventfs. They should both act the
same. They were different because of a misconception due to the
remount not resetting the flags. Now that remount resets all the
files and directories to default to the root node if a uid/gid is
specified, it makes the logic simpler to implement.

Beau Belgrave (2):
tracing/user_events: Fix non-spaced field matching
selftests/user_events: Add non-spacing separator check

Steven Rostedt (Google) (7):
eventfs/tracing: Add callback for release of an eventfs_inode
eventfs: Free all of the eventfs_inode after RCU
tracefs: Reset permissions on remount if permissions are options
tracefs: Still use mount point as default permissions for instances
eventfs: Do not differentiate the toplevel events directory
eventfs: Do not treat events directory different than other directories
eventfs: Have "events" directory get permissions from its parent

----
fs/tracefs/event_inode.c | 148 ++++++++++++++--------
fs/tracefs/inode.c | 92 +++++++++++++-
fs/tracefs/internal.h | 14 +-
include/linux/tracefs.h | 3 +
kernel/trace/trace_events.c | 12 ++
kernel/trace/trace_events_user.c | 76 ++++++++++-
tools/testing/selftests/user_events/ftrace_test.c | 8 ++
7 files changed, 293 insertions(+), 60 deletions(-)