From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- fs/notify/notification.c | 193 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 193 insertions(+) create mode 100644 fs/notify/notification.c (limited to 'fs/notify/notification.c') diff --git a/fs/notify/notification.c b/fs/notify/notification.c new file mode 100644 index 000000000..9022ae650 --- /dev/null +++ b/fs/notify/notification.c @@ -0,0 +1,193 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2008 Red Hat, Inc., Eric Paris + */ + +/* + * Basic idea behind the notification queue: An fsnotify group (like inotify) + * sends the userspace notification about events asynchronously some time after + * the event happened. When inotify gets an event it will need to add that + * event to the group notify queue. Since a single event might need to be on + * multiple group's notification queues we can't add the event directly to each + * queue and instead add a small "event_holder" to each queue. This event_holder + * has a pointer back to the original event. Since the majority of events are + * going to end up on one, and only one, notification queue we embed one + * event_holder into each event. This means we have a single allocation instead + * of always needing two. If the embedded event_holder is already in use by + * another group a new event_holder (from fsnotify_event_holder_cachep) will be + * allocated and used. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include +#include "fsnotify.h" + +static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0); + +/** + * fsnotify_get_cookie - return a unique cookie for use in synchronizing events. + * Called from fsnotify_move, which is inlined into filesystem modules. + */ +u32 fsnotify_get_cookie(void) +{ + return atomic_inc_return(&fsnotify_sync_cookie); +} +EXPORT_SYMBOL_GPL(fsnotify_get_cookie); + +void fsnotify_destroy_event(struct fsnotify_group *group, + struct fsnotify_event *event) +{ + /* Overflow events are per-group and we don't want to free them */ + if (!event || event == group->overflow_event) + return; + /* + * If the event is still queued, we have a problem... Do an unreliable + * lockless check first to avoid locking in the common case. The + * locking may be necessary for permission events which got removed + * from the list by a different CPU than the one freeing the event. + */ + if (!list_empty(&event->list)) { + spin_lock(&group->notification_lock); + WARN_ON(!list_empty(&event->list)); + spin_unlock(&group->notification_lock); + } + group->ops->free_event(group, event); +} + +/* + * Try to add an event to the notification queue. + * The group can later pull this event off the queue to deal with. + * The group can use the @merge hook to merge the event with a queued event. + * The group can use the @insert hook to insert the event into hash table. + * The function returns: + * 0 if the event was added to a queue + * 1 if the event was merged with some other queued event + * 2 if the event was not queued - either the queue of events has overflown + * or the group is shutting down. + */ +int fsnotify_insert_event(struct fsnotify_group *group, + struct fsnotify_event *event, + int (*merge)(struct fsnotify_group *, + struct fsnotify_event *), + void (*insert)(struct fsnotify_group *, + struct fsnotify_event *)) +{ + int ret = 0; + struct list_head *list = &group->notification_list; + + pr_debug("%s: group=%p event=%p\n", __func__, group, event); + + spin_lock(&group->notification_lock); + + if (group->shutdown) { + spin_unlock(&group->notification_lock); + return 2; + } + + if (event == group->overflow_event || + group->q_len >= group->max_events) { + ret = 2; + /* Queue overflow event only if it isn't already queued */ + if (!list_empty(&group->overflow_event->list)) { + spin_unlock(&group->notification_lock); + return ret; + } + event = group->overflow_event; + goto queue; + } + + if (!list_empty(list) && merge) { + ret = merge(group, event); + if (ret) { + spin_unlock(&group->notification_lock); + return ret; + } + } + +queue: + group->q_len++; + list_add_tail(&event->list, list); + if (insert) + insert(group, event); + spin_unlock(&group->notification_lock); + + wake_up(&group->notification_waitq); + kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); + return ret; +} + +void fsnotify_remove_queued_event(struct fsnotify_group *group, + struct fsnotify_event *event) +{ + assert_spin_locked(&group->notification_lock); + /* + * We need to init list head for the case of overflow event so that + * check in fsnotify_add_event() works + */ + list_del_init(&event->list); + group->q_len--; +} + +/* + * Return the first event on the notification list without removing it. + * Returns NULL if the list is empty. + */ +struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group) +{ + assert_spin_locked(&group->notification_lock); + + if (fsnotify_notify_queue_is_empty(group)) + return NULL; + + return list_first_entry(&group->notification_list, + struct fsnotify_event, list); +} + +/* + * Remove and return the first event from the notification list. It is the + * responsibility of the caller to destroy the obtained event + */ +struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group) +{ + struct fsnotify_event *event = fsnotify_peek_first_event(group); + + if (!event) + return NULL; + + pr_debug("%s: group=%p event=%p\n", __func__, group, event); + + fsnotify_remove_queued_event(group, event); + + return event; +} + +/* + * Called when a group is being torn down to clean up any outstanding + * event notifications. + */ +void fsnotify_flush_notify(struct fsnotify_group *group) +{ + struct fsnotify_event *event; + + spin_lock(&group->notification_lock); + while (!fsnotify_notify_queue_is_empty(group)) { + event = fsnotify_remove_first_event(group); + spin_unlock(&group->notification_lock); + fsnotify_destroy_event(group, event); + spin_lock(&group->notification_lock); + } + spin_unlock(&group->notification_lock); +} -- cgit v1.3.1