ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 86 insertions, 0 deletions

diff --git a/Documentation/filesystems/ecryptfs.rst b/Documentation/filesystems/ecryptfs.rst
new file mode 100644
index 000000000..1f2edef4c
--- /dev/null
+++ b/Documentation/filesystems/ecryptfs.rst
@@ -0,0 +1,86 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================================================
+eCryptfs: A stacked cryptographic filesystem for Linux
+======================================================
+
+eCryptfs is free software. Please see the file COPYING for details.
+For documentation, please see the files in the doc/ subdirectory.  For
+building and installation instructions please see the INSTALL file.
+
+:Maintainer: Phillip Hellewell
+:Lead developer: Michael A. Halcrow <mhalcrow@us.ibm.com>
+:Developers: Michael C. Thompson
+             Kent Yoder
+:Web Site: http://ecryptfs.sf.net
+
+This software is currently undergoing development. Make sure to
+maintain a backup copy of any data you write into eCryptfs.
+
+eCryptfs requires the userspace tools downloadable from the
+SourceForge site:
+
+http://sourceforge.net/projects/ecryptfs/
+
+Userspace requirements include:
+
+- David Howells' userspace keyring headers and libraries (version
+  1.0 or higher), obtainable from
+  http://people.redhat.com/~dhowells/keyutils/
+- Libgcrypt
+
+
+.. note::
+
+   In the beta/experimental releases of eCryptfs, when you upgrade
+   eCryptfs, you should copy the files to an unencrypted location and
+   then copy the files back into the new eCryptfs mount to migrate the
+   files.
+
+
+Mount-wide Passphrase
+=====================
+
+Create a new directory into which eCryptfs will write its encrypted
+files (i.e., /root/crypt).  Then, create the mount point directory
+(i.e., /mnt/crypt).  Now it's time to mount eCryptfs::
+
+    mount -t ecryptfs /root/crypt /mnt/crypt
+
+You should be prompted for a passphrase and a salt (the salt may be
+blank).
+
+Try writing a new file::
+
+    echo "Hello, World" > /mnt/crypt/hello.txt
+
+The operation will complete.  Notice that there is a new file in
+/root/crypt that is at least 12288 bytes in size (depending on your
+host page size).  This is the encrypted underlying file for what you
+just wrote.  To test reading, from start to finish, you need to clear
+the user session keyring:
+
+keyctl clear @u
+
+Then umount /mnt/crypt and mount again per the instructions given
+above.
+
+::
+
+    cat /mnt/crypt/hello.txt
+
+
+Notes
+=====
+
+eCryptfs version 0.1 should only be mounted on (1) empty directories
+or (2) directories containing files only created by eCryptfs. If you
+mount a directory that has pre-existing files not created by eCryptfs,
+then behavior is undefined. Do not run eCryptfs in higher verbosity
+levels unless you are doing so for the sole purpose of debugging or
+development, since secret values will be written out to the system log
+in that case.
+
+
+Mike Halcrow
+mhalcrow@us.ibm.com