From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- drivers/android/binder/context.rs | 175 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 175 insertions(+) create mode 100644 drivers/android/binder/context.rs (limited to 'drivers/android/binder/context.rs') diff --git a/drivers/android/binder/context.rs b/drivers/android/binder/context.rs new file mode 100644 index 000000000..ddddb66b3 --- /dev/null +++ b/drivers/android/binder/context.rs @@ -0,0 +1,175 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2025 Google LLC. + +use kernel::{ + alloc::kvec::KVVec, + error::code::*, + prelude::*, + security, + str::{CStr, CString}, + sync::{Arc, Mutex}, + task::Kuid, +}; + +use crate::{error::BinderError, node::NodeRef, process::Process}; + +kernel::sync::global_lock! { + // SAFETY: We call `init` in the module initializer, so it's initialized before first use. + pub(crate) unsafe(uninit) static CONTEXTS: Mutex = ContextList { + contexts: KVVec::new(), + }; +} + +pub(crate) struct ContextList { + contexts: KVVec>, +} + +pub(crate) fn get_all_contexts() -> Result>> { + let lock = CONTEXTS.lock(); + let mut ctxs = KVVec::with_capacity(lock.contexts.len(), GFP_KERNEL)?; + for ctx in lock.contexts.iter() { + ctxs.push(ctx.clone(), GFP_KERNEL)?; + } + Ok(ctxs) +} + +/// This struct keeps track of the processes using this context, and which process is the context +/// manager. +struct Manager { + node: Option, + uid: Option, + all_procs: KVVec>, +} + +/// There is one context per binder file (/dev/binder, /dev/hwbinder, etc) +#[pin_data] +pub(crate) struct Context { + #[pin] + manager: Mutex, + pub(crate) name: CString, +} + +impl Context { + pub(crate) fn new(name: &CStr) -> Result> { + let name = CString::try_from(name)?; + let ctx = Arc::pin_init( + try_pin_init!(Context { + name, + manager <- kernel::new_mutex!(Manager { + all_procs: KVVec::new(), + node: None, + uid: None, + }, "Context::manager"), + }), + GFP_KERNEL, + )?; + + CONTEXTS.lock().contexts.push(ctx.clone(), GFP_KERNEL)?; + + Ok(ctx) + } + + /// Called when the file for this context is unlinked. + /// + /// No-op if called twice. + pub(crate) fn deregister(self: &Arc) { + // Safe removal using retain + CONTEXTS.lock().contexts.retain(|c| !Arc::ptr_eq(c, self)); + } + + pub(crate) fn register_process(self: &Arc, proc: Arc) -> Result { + if !Arc::ptr_eq(self, &proc.ctx) { + pr_err!("Context::register_process called on the wrong context."); + return Err(EINVAL); + } + self.manager.lock().all_procs.push(proc, GFP_KERNEL)?; + Ok(()) + } + + pub(crate) fn deregister_process(self: &Arc, proc: &Arc) { + if !Arc::ptr_eq(self, &proc.ctx) { + pr_err!("Context::deregister_process called on the wrong context."); + return; + } + let mut manager = self.manager.lock(); + manager.all_procs.retain(|p| !Arc::ptr_eq(p, proc)); + + // Shrink the vector if it has significant unused capacity to avoid memory waste, + // but use a conservative strategy to prevent shrink-then-regrow oscillation. + // Only shrink when length drops below 1/4 of capacity, and shrink to twice the length. + let len = manager.all_procs.len(); + let cap = manager.all_procs.capacity(); + if len < cap / 4 { + // Shrink to twice the current length. Ignore allocation failures since this + // is just an optimization; the vector remains valid even if shrinking fails. + let _ = manager.all_procs.shrink_to(len * 2, GFP_KERNEL); + } + } + + pub(crate) fn set_manager_node(&self, node_ref: NodeRef) -> Result { + let mut manager = self.manager.lock(); + if manager.node.is_some() { + pr_warn!("BINDER_SET_CONTEXT_MGR already set"); + return Err(EBUSY); + } + security::binder_set_context_mgr(&node_ref.node.owner.cred)?; + + // If the context manager has been set before, ensure that we use the same euid. + let caller_uid = Kuid::current_euid(); + if let Some(ref uid) = manager.uid { + if *uid != caller_uid { + return Err(EPERM); + } + } + + manager.node = Some(node_ref); + manager.uid = Some(caller_uid); + Ok(()) + } + + pub(crate) fn unset_manager_node(&self) { + let node_ref = self.manager.lock().node.take(); + drop(node_ref); + } + + pub(crate) fn get_manager_node(&self, strong: bool) -> Result { + self.manager + .lock() + .node + .as_ref() + .ok_or_else(BinderError::new_dead)? + .clone(strong) + .map_err(BinderError::from) + } + + pub(crate) fn for_each_proc(&self, mut func: F) + where + F: FnMut(&Process), + { + let lock = self.manager.lock(); + for proc in &lock.all_procs { + func(proc); + } + } + + pub(crate) fn get_all_procs(&self) -> Result>> { + let lock = self.manager.lock(); + let mut procs = KVVec::with_capacity(lock.all_procs.len(), GFP_KERNEL)?; + for proc in lock.all_procs.iter() { + procs.push(Arc::clone(proc), GFP_KERNEL)?; + } + Ok(procs) + } + + pub(crate) fn get_procs_with_pid(&self, pid: i32) -> Result>> { + let lock = self.manager.lock(); + let mut matching_procs = KVVec::new(); + for proc in lock.all_procs.iter() { + if proc.task.pid() == pid { + matching_procs.push(Arc::clone(proc), GFP_KERNEL)?; + } + } + Ok(matching_procs) + } +} -- cgit v1.3.1