[GIT PULL] tracing: Fixes for 7.2
From: Steven Rostedt
Date: Sun Aug 09 2026 - 11:32:59 EST
Linus,
tracing fixes for 7.2:
- Fix use-after-free in eventfs_remove_rec()
The freeing of the eventfs_inode children used list_for_each_entry() where
the child is freed via srcu, but there's still a chance that it gets freed.
It should be using list_for_each_entry_safe().
- Fix eventfs_inode SRCU use of list in freeing
The iterator uses an SRCU protected list walk on the eventfs inodes. The
eventfs inode uses its "list" field in a union with the RCU list head.
When the inode gets added to the SRCU list it immediately corrupts the
list pointer and can cause an issue with the iterator. Move the RCU list
head to be shared with the children list head which allows the iterator to
check the parent inode if is freed before referencing the child. Have the
iterator check the parent "is_freed" field and break out if it is set.
Also add memory barriers to make sure the ordering is correct.
- Fix various RCU synchronization issues with direct_functions
Updates to direct_functions have some missing RCU protection and
synchronization. Restructure the code a bit to make sure updates to the
direct_functions are protected.
- Remove an unneeded comma from a scope_guard()
There's a spurious comma in a scope_guard(). Remove it.
- Fix race in per CPU buffer swap in the ring buffer
When a per CPU buffer swap happens, it must make sure that it doesn't
occur while a writer is active. Instead it returns an -EBUSY. But there's
a small race window when a writer moves from one sub-buffer to the next
that it resets the "committing" counter. If a swap happens at that moment,
the buffer used for the commit of an event will not match the buffer the
event is actually on. Instead of using the "committing" counter, use the
recursive detection counter that does not get reset when the writer
crosses sub-buffers.
- Fix off-by-one in ftrace_free_mem()
The function ftrace_free_mem() gets an "end_ptr" as a parameter that is
exclusive to the rang to be freed. But its value is used to search for the
records that expects an inclusive value. Subtract one from the parameter
to convert it to an inclusive range.
- Disable resizing of the ring buffer for persistent buffers
Resizing the persistent buffer has undefined behavior. Prevent it from
being resized.
- Disable changing ring buffer subbuf order when resizing is disabled
The ring buffer subbuffer order can not be changed during resizing. Use
that instead of just checking if the buffer is mapped as mapped buffers
also have resizing disabled.
- Initialize subbuf_order of reader pages when they are created
In rb_allocate_cpu_buffer() the bpage->order is not updated to the current
subbuf_order leaving it as zero. This value is used when the page is freed.
- Fix test_ringbuffer() to test for ERR_PTR before calling kthread_stop()
The rb_threads[] array is assigned the output of kthread_run_on_cpu()
which could return an ERR_PTR. At the end of the test, all threads in the
array are cleaned up by kthread_stop() passing in the value in the array
if it isn't zero. But if the array contains an ERR_PTR, kthread_stop()
will not be able to handle it properly.
Please pull the latest trace-v7.2-rc6 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace-v7.2-rc6
Tag SHA1: 45eb4670a102b91101fcd1e3cf1fd33bbca79ab9
Head SHA1: 91542863abade2fd4f2b361991f5386ad9d19c8c
Hui Su (1):
ring-buffer: Fix crash passing ERR_PTR to kthread_stop()
Josh Poimboeuf (1):
ftrace: Fix off-by-one fentry site disable in ftrace_free_mem()
Leon Hwang (4):
ftrace: Protect direct_functions in ftrace_find_rec_direct
ftrace: Protect direct_functions in update_ftrace_direct_del
ftrace: Protect direct_functions in update_ftrace_direct_mod
ftrace: Drop extra comma in trace_buffered_event_enable
Shuangpeng Bai (1):
eventfs: Fix use-after-free in eventfs_remove_rec()
Steven Rostedt (1):
eventfs: Use children field for rcu head and add memory barriers
Tengda Wu (1):
ring-buffer: Use current_context for safe per-CPU buffer swap
Vincent Donnefort (3):
ring-buffer: Prevent resizing of persistent ring buffer
ring-buffer: Prevent subbuf order change when resizing is disabled
ring-buffer: Initialise reader page order in rb_allocate_cpu_buffer()
----
fs/tracefs/event_inode.c | 28 ++++++++++++++++++++++++++--
fs/tracefs/internal.h | 4 ++--
kernel/trace/ftrace.c | 33 +++++++++++++++++++++++----------
kernel/trace/ring_buffer.c | 15 +++++++++------
kernel/trace/trace.c | 2 +-
5 files changed, 61 insertions(+), 21 deletions(-)
---------------------------
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 39c7a34531e8..a52458435327 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -124,7 +124,17 @@ static inline void put_ei(struct eventfs_inode *ei)
static inline void free_ei(struct eventfs_inode *ei)
{
if (ei) {
+ /* The ei should have no children if it is being freed. */
+ WARN_ON_ONCE(!list_empty(&ei->children));
ei->is_freed = 1;
+ /*
+ * The SRCU iteration has a smp_rmb() to make sure it
+ * sees a child (that may have already been freed)
+ * before it reads is_free. If is_free is set, it must
+ * not use the child it acquired from ei->children, as
+ * the list may be used for SRCU.
+ */
+ smp_wmb();
put_ei(ei);
}
}
@@ -627,6 +637,20 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx)
list_for_each_entry_srcu(ei_child, &ei->children, list,
srcu_read_lock_held(&eventfs_srcu)) {
+ /*
+ * If the ei is being freed, then the ei->children may be
+ * being used as the rcu list, which means the next element
+ * may be garbage. The ei->is_free is set before switching
+ * the ei->children over to ei->rcu. The read memory barrier
+ * here makes sure the ei_child is read before is_free is
+ * updated.
+ *
+ * Matches the smp_wmb() in free_ei()
+ */
+ smp_rmb();
+ if (ei->is_freed)
+ return -EINVAL;
+
if (c > 0) {
c--;
continue;
@@ -822,7 +846,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
*/
static void eventfs_remove_rec(struct eventfs_inode *ei, int level)
{
- struct eventfs_inode *ei_child;
+ struct eventfs_inode *ei_child, *tmp;
/*
* Check recursion depth. It should never be greater than 3:
@@ -835,7 +859,7 @@ static void eventfs_remove_rec(struct eventfs_inode *ei, int level)
return;
/* search for nested folders or files */
- list_for_each_entry(ei_child, &ei->children, list)
+ list_for_each_entry_safe(ei_child, tmp, &ei->children, list)
eventfs_remove_rec(ei_child, level + 1);
list_del_rcu(&ei->list);
diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h
index a4a7f8431aff..c61481d04c8e 100644
--- a/fs/tracefs/internal.h
+++ b/fs/tracefs/internal.h
@@ -46,11 +46,11 @@ struct eventfs_attr {
* @ino: The saved inode number
*/
struct eventfs_inode {
+ struct list_head list;
union {
- struct list_head list;
+ struct list_head children;
struct rcu_head rcu;
};
- struct list_head children;
const struct eventfs_entry *entries;
const char *name;
struct eventfs_attr *entry_attrs;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 6c47a94f5924..7c50f8ae5a0c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2645,7 +2645,8 @@ unsigned long ftrace_find_rec_direct(unsigned long ip)
{
struct ftrace_func_entry *entry;
- entry = __ftrace_lookup_ip(direct_functions, ip);
+ guard(preempt_notrace)();
+ entry = __ftrace_lookup_ip(rcu_dereference_sched(direct_functions), ip);
if (!entry)
return 0;
@@ -6511,6 +6512,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
struct ftrace_hash *new_direct_functions;
struct ftrace_hash *new_filter_hash = NULL;
struct ftrace_hash *old_filter_hash;
+ struct ftrace_hash *direct_hash;
struct ftrace_func_entry *entry;
struct ftrace_func_entry *del;
unsigned long size;
@@ -6522,11 +6524,13 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
return -EINVAL;
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return -EINVAL;
- if (direct_functions == EMPTY_HASH)
- return -EINVAL;
mutex_lock(&direct_mutex);
+ direct_hash = rcu_dereference_protected(direct_functions, lockdep_is_held(&direct_mutex));
+ if (direct_hash == EMPTY_HASH)
+ goto out_unlock;
+
old_filter_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL;
if (!hash_count(old_filter_hash))
@@ -6536,7 +6540,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
size = 1 << hash->size_bits;
for (int i = 0; i < size; i++) {
hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
- del = __ftrace_lookup_ip(direct_functions, entry->ip);
+ del = __ftrace_lookup_ip(direct_hash, entry->ip);
if (!del || del->direct != entry->direct)
goto out_unlock;
}
@@ -6547,7 +6551,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
if (!new_filter_hash)
goto out_unlock;
- new_direct_functions = hash_sub(direct_functions, hash);
+ new_direct_functions = hash_sub(direct_hash, hash);
if (!new_direct_functions)
goto out_unlock;
@@ -6574,7 +6578,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
/* free the new_direct_functions */
old_direct_functions = new_direct_functions;
} else {
- old_direct_functions = direct_functions;
+ old_direct_functions = direct_hash;
rcu_assign_pointer(direct_functions, new_direct_functions);
}
@@ -6613,6 +6617,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
.func = ftrace_stub,
.flags = FTRACE_OPS_FL_STUB,
};
+ struct ftrace_hash *direct_hash;
struct ftrace_hash *orig_hash;
unsigned long size, i;
int err = -EINVAL;
@@ -6623,8 +6628,6 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
return -EINVAL;
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return -EINVAL;
- if (direct_functions == EMPTY_HASH)
- return -EINVAL;
/*
* We can be called from within ops_func callback with direct_mutex
@@ -6632,6 +6635,12 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
*/
if (do_direct_lock)
mutex_lock(&direct_mutex);
+ else
+ lockdep_assert_held_once(&direct_mutex);
+
+ direct_hash = rcu_dereference_protected(direct_functions, lockdep_is_held(&direct_mutex));
+ if (direct_hash == EMPTY_HASH)
+ goto unlock;
orig_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL;
if (!orig_hash)
@@ -6663,7 +6672,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
size = 1 << hash->size_bits;
for (i = 0; i < size; i++) {
hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
- tmp = __ftrace_lookup_ip(direct_functions, entry->ip);
+ tmp = __ftrace_lookup_ip(direct_hash, entry->ip);
if (!tmp)
continue;
tmp->direct = entry->direct;
@@ -8296,7 +8305,8 @@ static void add_to_clear_hash_list(struct list_head *clear_list,
void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
{
unsigned long start = (unsigned long)(start_ptr);
- unsigned long end = (unsigned long)(end_ptr);
+ /* end is inclusive and end_ptr is exclusive */
+ unsigned long end = (unsigned long)(end_ptr) - 1;
struct ftrace_page **last_pg = &ftrace_pages_start;
struct ftrace_page *tmp_page = NULL;
struct ftrace_page *pg;
@@ -8306,6 +8316,9 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
struct ftrace_init_func *func, *func_next;
LIST_HEAD(clear_hash);
+ if (start_ptr >= end_ptr)
+ return;
+
key.ip = start;
key.flags = end; /* overload flags, as it is unsigned long */
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 8e2485bb3aa8..2667992f0aa2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2510,6 +2510,7 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
bpage = alloc_cpu_page(cpu);
if (!bpage)
return NULL;
+ bpage->order = cpu_buffer->buffer->subbuf_order;
rb_check_bpage(cpu_buffer, bpage);
@@ -2528,6 +2529,8 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
if (cpu_buffer->ring_meta->head_buffer)
rb_meta_buffer_update(cpu_buffer, bpage);
bpage->range = 1;
+
+ atomic_inc(&cpu_buffer->resize_disabled);
} else if (buffer->remote) {
struct ring_buffer_desc *desc = ring_buffer_desc(buffer->remote->desc, cpu);
@@ -6852,7 +6855,7 @@ int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
{
struct ring_buffer_per_cpu *cpu_buffer_a;
struct ring_buffer_per_cpu *cpu_buffer_b;
- int ret = -EINVAL;
+ int ret = -EBUSY;
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
!cpumask_test_cpu(cpu, buffer_b->cpumask))
@@ -6893,10 +6896,10 @@ int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
atomic_inc(&cpu_buffer_a->record_disabled);
atomic_inc(&cpu_buffer_b->record_disabled);
- ret = -EBUSY;
- if (local_read(&cpu_buffer_a->committing))
+ /* Do not swap if either buffer is in the process of writing */
+ if (cpu_buffer_a->current_context)
goto out_dec;
- if (local_read(&cpu_buffer_b->committing))
+ if (cpu_buffer_b->current_context)
goto out_dec;
/*
@@ -7358,7 +7361,7 @@ int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
cpu_buffer = buffer->buffers[cpu];
- if (cpu_buffer->mapped) {
+ if (atomic_read(&cpu_buffer->resize_disabled)) {
err = -EBUSY;
goto error;
}
@@ -8214,7 +8217,7 @@ static __init int test_ringbuffer(void)
out_free:
for_each_online_cpu(cpu) {
- if (!rb_threads[cpu])
+ if (IS_ERR_OR_NULL(rb_threads[cpu]))
break;
kthread_stop(rb_threads[cpu]);
}
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 01a5e87af299..395238b2b715 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1788,7 +1788,7 @@ void trace_buffered_event_enable(void)
per_cpu(trace_buffered_event, cpu) = event;
- scoped_guard(preempt,) {
+ scoped_guard(preempt) {
if (cpu == smp_processor_id() &&
__this_cpu_read(trace_buffered_event) !=
per_cpu(trace_buffered_event, cpu))