[for-linus][PATCH 01/12] eventfs: Fix use-after-free in eventfs_remove_rec()

[for-linus][PATCH 01/12] eventfs: Fix use-after-free in eventfs_remove_rec()

[Steven Rostedt]

From: Shuangpeng Bai <shuangpeng.kernel@gmail.com>

eventfs_remove_rec() recursively removes the child at the current loop
position. After the recursive call returns, list_for_each_entry() advances
by reading list.next from the removed child.

If free_ei() drops the final reference, release_ei() reuses the list/rcu
union to queue an SRCU callback. The child may be freed before that read.
The eventfs_mutex serializes list updates, but it does not keep the removed
child alive or prevent the SRCU callback from running.

Use list_for_each_entry_safe() to save the next sibling before recursively
removing the current child.

Cc: stable@vger.kernel.org
Fixes: 43aa6f97c2d0 ("eventfs: Get rid of dentry pointers without refcounts")
Link: https://patch.msgid.link/20260806022719.375354-1-shuangpeng.kernel@gmail.com
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 39c7a34531e8..93bc4f83b73e 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -822,7 +822,7 @@ 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 +835,7 @@ 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);
-- 
2.53.0

[for-linus][PATCH 02/12] eventfs: Use children field for rcu head and add memory barriers

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

When an eventfs inode is freed, it sets ei->is_freed and then uses its
ei->list to add it to the srcu link list as the list field is a union with
the rcu list head. As the ei->list is used to iterate over an SRCU
protected list without taking the eventfs_mutex, there's nothing stopping
the iteration over that list to see the ei->rcu instead of the ei->list
and it will read a corrupt target.

To fix this, change the union of the rcu list head with the children list.
On freeing the eventfs inode, set the is_free and execute a smp_wmb()
before adding the eventfs inode to the SRCU list.

On iteration of the ei->children list, at the start, execute a smp_rmb()
and then read the is_freed of the ei to see if the children list is still
valid. If is_freed is set, then the ei_child read is not valid and the
loop should exit immediately.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260808094215.4252430d@robin
Fixes: 704f960dbee2f ("eventfs: Read ei->entries before ei->children in eventfs_iterate()")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260806022719.375354-1-shuangpeng.kernel%40gmail.com
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 fs/tracefs/event_inode.c | 24 ++++++++++++++++++++++++
 fs/tracefs/internal.h    |  4 ++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 93bc4f83b73e..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;
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;
-- 
2.53.0

[for-linus][PATCH 03/12] ftrace: Protect direct_functions in ftrace_find_rec_direct

[Steven Rostedt]

From: Leon Hwang <leon.hwang@linux.dev>

Fix accessing the __rcu pointer direct_functions with RCU protection.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260730150411.88667-2-leon.hwang@linux.dev
Fixes: d05cb470663a ("ftrace: Fix modification of direct_function hash while in use")
Acked-by: Jiri Olsa <jolsa@kernel.org>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 6c47a94f5924..c5d1d0d42ccc 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;
 
-- 
2.53.0

[for-linus][PATCH 04/12] ftrace: Protect direct_functions in update_ftrace_direct_del

[Steven Rostedt]

From: Leon Hwang <leon.hwang@linux.dev>

Fix accessing the __rcu pointer direct_functions with RCU protection.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260730150411.88667-3-leon.hwang@linux.dev
Fixes: 8d2c1233f371 ("ftrace: Add update_ftrace_direct_del function")
Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c5d1d0d42ccc..9ea39110927f 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6512,6 +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;
@@ -6523,11 +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))
@@ -6537,7 +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;
 		}
@@ -6548,7 +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;
 
@@ -6575,7 +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);
 	}
 
-- 
2.53.0

[for-linus][PATCH 05/12] ftrace: Protect direct_functions in update_ftrace_direct_mod

[Steven Rostedt]

From: Leon Hwang <leon.hwang@linux.dev>

Fix accessing the __rcu pointer direct_functions with RCU protection.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260730150411.88667-4-leon.hwang@linux.dev
Fixes: e93672f770d7 ("ftrace: Add update_ftrace_direct_mod function")
Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 9ea39110927f..414e425c2d80 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6617,6 +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;
@@ -6627,8 +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
@@ -6636,6 +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)
@@ -6667,7 +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;
-- 
2.53.0

[for-linus][PATCH 07/12] ring-buffer: Use current_context for safe per-CPU buffer swap

[Steven Rostedt]

From: Tengda Wu <wutengda@huaweicloud.com>

The ring_buffer_swap_cpu() function currently checks the per-CPU
committing counter to determine if a buffer is actively being written to
before performing the swap. However, there exists a race window where
this check can be bypassed:

    ring_buffer_lock_reserve
        cpu_buffer = buffer->buffers[cpu];       // cpu_buffer_a
        rb_reserve_next_event
            rb_start_commit // inc committing
            if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {...}
            __rb_reserve_next
                rb_move_tail
                    rb_end_commit(cpu_buffer);   // dec committing => 0
                    /* interrupt hits here, successfully swaps! */
                    local_inc(&cpu_buffer->committing);

    ring_buffer_unlock_commit
        cpu_buffer = buffer->buffers[cpu];      // cpu_buffer_b
        rb_commit
            rb_end_commit
            RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing))
                                                // triggers warning

The committing counter can temporarily drop to 0 during a single write
operation (within rb_move_tail), creating a window where swap can
succeed even though the write is still in progress. This leads to
inconsistent buffer state and triggers the RB_WARN_ON in rb_commit().

Replace the committing counter check with current_context checks, which
are set at the entry of ring_buffer_lock_reserve() and remain valid
throughout the entire write operation, providing a reliable indicator of
buffer busy state during swap.

Cc: stable@vger.kernel.org
Fixes: 4239c38fe0b3 ("ring-buffer: Process commits whenever moving to a new page.")
Link: https://patch.msgid.link/20260803005640.2445666-2-wutengda@huaweicloud.com
Signed-off-by: Tengda Wu <wutengda@huaweicloud.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 8e2485bb3aa8..58dc8995a88d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -6852,7 +6852,7 @@ 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 +6893,10 @@ 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;
 
 	/*
-- 
2.53.0

[for-linus][PATCH 08/12] ftrace: Fix off-by-one fentry site disable in ftrace_free_mem()

[Steven Rostedt]

From: Josh Poimboeuf <jpoimboe@kernel.org>

When a module's init text is freed, do_init_module() calls
ftrace_free_mem() with a half-open [start, end) range.  However the
ftrace_cmp_recs() comparator treats the upper bound as inclusive, as all
its other users do, passing 'ip + size - 1'.  So ftrace_free_mem() can
delete a record sitting exactly at 'end', which is outside the freed
range.

For a kernel without CFI or IBT, the first record of a function is at
the function start, which for the first function in a module is also the
base of its text allocation.  As the module allocator packs its regions,
that address is often the 'end' passed by a neighboring module's
do_init_module(), causing the first function's ftrace location to get
disabled, preventing an attempt to livepatch it:

  livepatch: failed to find location for function 'pcspkr_probe'

Convert the exclusive end to the inclusive 'end - 1' the comparator
expects, and return early for an empty range to avoid the subtraction
from underflowing when the init text size is zero.

Cc: stable@vger.kernel.org
Fixes: 42c269c88dc1 ("ftrace: Allow for function tracing to record init functions on boot up")
Link: https://patch.msgid.link/1b5ccfa8095bdb1277f84af1c2c2e2205aca03ae.1785992188.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 414e425c2d80..7c50f8ae5a0c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -8305,7 +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;
@@ -8315,6 +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 */
 
-- 
2.53.0

[for-linus][PATCH 09/12] ring-buffer: Prevent resizing of persistent ring buffer

[Steven Rostedt]

From: Vincent Donnefort <vdonnefort@google.com>

Dynamically resizing a persistent ring buffer is not possible. Disable
the feature.

Cc: stable@vger.kernel.org
Fixes: be68d63a139b ("ring-buffer: Add ring_buffer_alloc_range()")
Link: https://patch.msgid.link/20260806211306.3704194-2-vdonnefort@google.com
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 58dc8995a88d..09d502ef4c55 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2528,6 +2528,8 @@ 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);
 
-- 
2.53.0

[for-linus][PATCH 10/12] ring-buffer: Prevent subbuf order change when resizing is disabled

[Steven Rostedt]

From: Vincent Donnefort <vdonnefort@google.com>

Because ring_buffer_subbuf_order_set() frees buffer pages, we can't
allow it when resizing is disabled. A non-consuming reader is at risk of
use-after-free (rb_advance_iter()).

Return -EBUSY on resize_disabled, matching ring_buffer_resize()
behaviour.

Cc: stable@vger.kernel.org
Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page")
Link: https://patch.msgid.link/20260806211306.3704194-3-vdonnefort@google.com
Reported-by: syzbot+e0cc44465d6bae735679@syzkaller.appspotmail.com
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 09d502ef4c55..6cbd80ccef37 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -7360,7 +7360,7 @@ 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;
 		}
-- 
2.53.0

[for-linus][PATCH 11/12] ring-buffer: Initialise reader page order in rb_allocate_cpu_buffer()

[Steven Rostedt]

From: Vincent Donnefort <vdonnefort@google.com>

In rb_allocate_cpu_buffer(), bpage->order was omitted, leaving it as 0.
This is an issue for a ring-buffer with subbufs bigger than PAGE_SIZE if
when freed: free_buffer_page() relies on this value. Align the value
with the actual allocation size (buffer::subbuf_order).

Cc: stable@vger.kernel.org
Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page")
Link: https://patch.msgid.link/20260806211306.3704194-4-vdonnefort@google.com
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 6cbd80ccef37..760a00e8505c 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);
 
-- 
2.53.0

[for-linus][PATCH 12/12] ring-buffer: Fix crash passing ERR_PTR to kthread_stop()

[Steven Rostedt]

From: Hui Su <sh_def@163.com>

In test_ringbuffer()'s out_free cleanup loop, the check
`!rb_threads[cpu]` only catches NULL entries and misses entries that
hold an ERR_PTR.

rb_threads[] is static, so unassigned slots are NULL. But when
kthread_run_on_cpu() fails for a cpu, it stores ERR_PTR(-ENOMEM) (or
-EINTR) in rb_threads[cpu] before the creation loop jumps to out_free.
That entry is non-NULL, so the old `!ptr` check does not break, and the
cleanup proceeds to call kthread_stop() on the ERR_PTR. kthread_stop()
then dereferences the bogus pointer, crashing the kernel during the
late_initcall self-test.

crash logs:
  BUG: kernel NULL pointer dereference, address: 000000000000001c
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 1 Comm: swapper/0 Not tainted 7.2.0-rc6-dirty #7 PREEMPT(lazy)
  RIP: 0010:kthread_stop+0x2e/0x220
  RBX: fffffffffffffff4
  CR2: 000000000000001c
  Call Trace:
   <TASK>
   test_ringbuffer+0x1ec/0x650
   do_one_initcall+0x6c/0x2c0
   kernel_init_freeable+0x21d/0x420
   kernel_init+0x15/0x1c0
   ret_from_fork+0x21b/0x320
   </TASK>
  Kernel panic - not syncing: Fatal exception

Cc: stable@vger.kernel.org
Fixes: 64ed3a049e3e ("ring-buffer: make use of the helper function kthread_run_on_cpu()")
Link: https://patch.msgid.link/20260807154145.2846521-2-sh_def@163.com
Signed-off-by: Hui Su <sh_def@163.com>
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 760a00e8505c..2667992f0aa2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -8217,7 +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]);
 	}
-- 
2.53.0