From a9a01be2834a529cbd490ccbab02643f0c1735f2 Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Fri, 7 Aug 2026 09:54:23 +0100 Subject: [PATCH 01/10] tracing: Fix logged instance name on creation failure When boot instance creation fails, the kernel incorrectly logs "(null)" as the instance name because strsep() consumes curr_str entirely during parsing. Print the properly parsed name variable instead. And while at it log the error code. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260807085423.4175161-1-vdonnefort@google.com Fixes: cb1f98c5e574 ("tracing: Add creation of instances at boot command line") Acked-by: Masami Hiramatsu (Google) Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 89dc1c0ebb90..740c5f358b75 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -9726,7 +9726,8 @@ __init static void enable_instances(void) tr = trace_array_create_systems(name, NULL, addr, size); if (IS_ERR(tr)) { - pr_warn("Tracing: Failed to create instance buffer %s\n", curr_str); + pr_warn("Tracing: Failed to create instance buffer '%s' (%ld)\n", name, + PTR_ERR(tr)); continue; } From a7318172aa332a161fb9618286e64454c827f8fd Mon Sep 17 00:00:00 2001 From: Hui Su Date: Sun, 16 Aug 2026 18:04:29 +0800 Subject: [PATCH 02/10] tracing: Fix use-after-free with same-name named triggers When two hist triggers on different events are registered with the same name=, the second one reuses the first as named_data. Both are added to tr->hist_vars by save_hist_vars() during event_hist_trigger_parse(), because save_hist_vars() is called before event_trigger_register() while the named reuse is only detected later, in hist_register_trigger(). In the named-data branch hist_register_trigger() then frees the second histogram's hist_data via destroy_hist_data(), but never removes its tr->hist_vars list entry, leaving a dangling pointer and leaking the trace_array reference it holds. A later hist trigger that references a variable makes find_var_file() walk tr->hist_vars and dereference the freed hist_data. The bug is reproducible from userspace by writing three hist triggers to tracefs: cd /sys/kernel/tracing echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_switch/trigger echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_process_fork/trigger echo 'hist:keys=common_pid:vals=$x' > events/sched/sched_process_exit/trigger The third write panics the kernel: BUG: KASAN: slab-use-after-free in find_var_file.part.0+0x272/0x290 Read of size 8 at addr ffff888001f8a0e0 by task sh/1 CPU: 1 UID: 0 PID: 1 Comm: sh Tainted: G D N Call Trace: find_var_file.part.0 find_event_var parse_atom parse_expr __create_val_field event_hist_trigger_parse trigger_process_regex event_trigger_write vfs_write ksys_write do_syscall_64 entry_SYSCALL_64_after_hwframe Allocated by task 1: event_hist_trigger_parse Freed by task 1: hist_register_trigger+0x618/0xa30 event_hist_trigger_parse The buggy address belongs to freed 2048-byte region Oops: general protection fault ... RIP: find_var_file.part.0 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b Fix by removing the hist_data from tr->hist_vars and releasing the trace_array reference in the named-data branch of hist_register_trigger() before freeing the hist_data. Cc: stable@vger.kernel.org Fixes: 6f86bdeab633 ("tracing: Fix bad hist from corrupting named_triggers list") Link: https://patch.msgid.link/20260816100427.33642-3-sh_def@163.com Signed-off-by: Hui Su Signed-off-by: Steven Rostedt --- kernel/trace/trace_events_hist.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 893bd8b0e48a..963e0d6b61fd 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -6661,8 +6661,10 @@ static int hist_register_trigger(char *glob, tracing_set_filter_buffering(file->tr, true); } - if (named_data) + if (named_data) { + remove_hist_vars(hist_data); destroy_hist_data(hist_data); + } out: return ret; } From 649bc7df3e5d7be6f7996a95084037dbf3cad1e5 Mon Sep 17 00:00:00 2001 From: Hui Su Date: Mon, 17 Aug 2026 20:06:44 +0800 Subject: [PATCH 03/10] tracing: Fix crash passing ERR_PTR to kthread_stop() event_test_stuff() calls kthread_run() and unconditionally passes the returned task_struct pointer to kthread_stop(). kthread_run() returns an error pointer such as ERR_PTR(-ENOMEM) when kthread creation fails, for example under memory pressure during the boot-time event self-test. kthread_stop() then dereferences the invalid pointer, crashing the kernel. Check the result of kthread_run() before passing it to kthread_stop(). Use WARN_ON() so that a failure to create the self-test thread does not go unnoticed, matching the ring-buffer self-test fix in commit 91542863abad ("ring-buffer: Fix crash passing ERR_PTR to kthread_stop()"). Cc: stable@vger.kernel.org Fixes: e6187007d6c3 ("tracing/events: add startup tests for events") Link: https://patch.msgid.link/20260817120642.668375-3-sh_def@163.com Signed-off-by: Hui Su Signed-off-by: Steven Rostedt --- kernel/trace/trace_events.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 9f8f2d02276c..1d39eaf6a0f7 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -5019,6 +5019,8 @@ static __init void event_test_stuff(void) struct task_struct *test_thread; test_thread = kthread_run(event_test_thread, NULL, "test-events"); + if (WARN_ON(IS_ERR(test_thread))) + return; msleep(1); kthread_stop(test_thread); } From 372f8534244d632ad5118e8a87a11291b01712d3 Mon Sep 17 00:00:00 2001 From: Deepanshu Kartikey Date: Mon, 17 Aug 2026 19:36:55 +0530 Subject: [PATCH 04/10] tracing: Fix use-after-free in trace_pipe read on sub-buffer order change Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page, and replaces them with newly allocated ones. Readers of trace_pipe hold pointers into those pages. ring_buffer_peek() looks up an event under cpu_buffer->reader_lock but returns the event pointer after dropping the lock, and peek_next_entry() then calls ring_buffer_event_length() and ring_buffer_event_data() on it. If the sub-buffer order is changed in that window, the reader dereferences freed memory: BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430 Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002 Freed by: free_buffer_page kernel/trace/ring_buffer.c:398 [inline] ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444 buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221 Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change. This is the lock trace_pipe readers already hold across their entire peek-and-print loop, so the swap can no longer race with a reader that is dereferencing a peeked event. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260817140655.5694-1-kartikey406@gmail.com Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page") Reported-by: syzbot+685955db58555575fdd2@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=685955db58555575fdd2 Tested-by: syzbot+685955db58555575fdd2@syzkaller.appspotmail.com Reviewed-by: Bradley Morgan Signed-off-by: Deepanshu Kartikey Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 740c5f358b75..60c87977f1e3 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8214,6 +8214,8 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf, /* Do not allow tracing while changing the order of the ring buffer */ tracing_stop_tr(tr); + trace_access_lock(RING_BUFFER_ALL_CPUS); + old_order = ring_buffer_subbuf_order_get(tr->array_buffer.buffer); if (old_order == order) goto out; @@ -8253,6 +8255,7 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf, #endif (*ppos)++; out: + trace_access_unlock(RING_BUFFER_ALL_CPUS); if (ret) cnt = ret; tracing_start_tr(tr); From 1704aaaf5d22bc765c168402350d191e24e245bc Mon Sep 17 00:00:00 2001 From: Deepanshu Kartikey Date: Mon, 24 Aug 2026 20:16:53 +0530 Subject: [PATCH 05/10] eventfs: Initialize ei->children and ei->list in init_ei() eventfs_create_dir() allocates the eventfs_inode and initializes it with init_ei(). But this does not initialize the eventfs_inode list_heads. If the eventfs_create_dir() fails due to memory pressure, it will call free_ei() before it initialized the lists, and that checks to make sure the eventfs_inode has no children. But because the list wasn't initialized, it will give a false warning. Fix it by moving the list initialization into init_ei(). Cc: stable@vger.kernel.org Fixes: 5790b1fb3d67 ("eventfs: Remove eventfs_file and just use eventfs_inode") Reported-by: syzbot+3ef80b4ed02226d04a06@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3ef80b4ed02226d04a06 Link: https://patch.msgid.link/20260824144653.54044-1-kartikey406@gmail.com Signed-off-by: Deepanshu Kartikey [ Rewrote change log ] Signed-off-by: Steven Rostedt --- fs/tracefs/event_inode.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 604ba3e841d2..6e3513b13cfa 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -438,6 +438,8 @@ static inline struct eventfs_inode *init_ei(struct eventfs_inode *ei, const char if (!ei->name) return NULL; kref_init(&ei->kref); + INIT_LIST_HEAD(&ei->children); + INIT_LIST_HEAD(&ei->list); return ei; } @@ -729,8 +731,6 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode ei->entries = entries; ei->nr_entries = size; ei->data = data; - INIT_LIST_HEAD(&ei->children); - INIT_LIST_HEAD(&ei->list); scoped_guard(mutex, &eventfs_mutex) { if (!parent->is_freed) @@ -802,9 +802,6 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry ei->attr.uid = uid; ei->attr.gid = gid; - INIT_LIST_HEAD(&ei->children); - INIT_LIST_HEAD(&ei->list); - ti = get_tracefs(inode); ti->flags |= TRACEFS_EVENT_INODE; ti->private = ei; From d79fb758e7e2e7a181eab630c0545a56041c473d Mon Sep 17 00:00:00 2001 From: Haotian Zhang Date: Wed, 26 Aug 2026 09:50:34 +0800 Subject: [PATCH 06/10] samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify ftrace_direct_init() assigns kthread_run()'s return value to simple_tsk without an IS_ERR() check. When kthread_run() fails it returns ERR_PTR(-ENOMEM), but init still returns 0, so the module loads with simple_tsk holding an error pointer. On unload, ftrace_direct_exit() then passes that ERR_PTR to kthread_stop(), leading to a null-pointer-dereference. Check the return value of kthread_run() with IS_ERR(); on failure, unregister the ftrace direct call and propagate the error code. Link: https://patch.msgid.link/20260826015034.10755-1-vulab@iscas.ac.cn Fixes: ae0cc3b7e7f5 ("ftrace/samples: Add a sample module that implements modify_ftrace_direct()") Suggested-by: Steven Rostedt Signed-off-by: Haotian Zhang Signed-off-by: Steven Rostedt --- samples/ftrace/ftrace-direct-modify.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c index 1ba1927b548e..164d9dd6fd92 100644 --- a/samples/ftrace/ftrace-direct-modify.c +++ b/samples/ftrace/ftrace-direct-modify.c @@ -320,9 +320,15 @@ static int __init ftrace_direct_init(void) ftrace_set_filter_ip(&direct, (unsigned long) my_ip, 0, 0); ret = register_ftrace_direct(&direct, my_tramp); - if (!ret) - simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); - return ret; + if (ret) + return ret; + simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); + if (IS_ERR(simple_tsk)) { + unregister_ftrace_direct(&direct, my_tramp, true); + return PTR_ERR(simple_tsk); + } + + return 0; } static void __exit ftrace_direct_exit(void) From 6727b7618f49401acf373fa3ec5712e2ec52e5cf Mon Sep 17 00:00:00 2001 From: Haotian Zhang Date: Wed, 26 Aug 2026 09:50:50 +0800 Subject: [PATCH 07/10] samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify ftrace_direct_multi_init() assigns kthread_run()'s return value to simple_tsk without an IS_ERR() check. When kthread_run() fails it returns ERR_PTR(-ENOMEM), but init still returns 0, so the module loads with simple_tsk holding an error pointer. On unload, ftrace_direct_multi_exit() then passes that ERR_PTR to kthread_stop(), leading to a null-pointer-dereference. Check the return value of kthread_run() with IS_ERR(); on failure, unregister the ftrace direct call and propagate the error code. Link: https://patch.msgid.link/20260826015050.10772-1-vulab@iscas.ac.cn Fixes: e1067a07cfbc ("ftrace/samples: Add module to test multi direct modify interface") Suggested-by: Steven Rostedt Signed-off-by: Haotian Zhang Signed-off-by: Steven Rostedt --- samples/ftrace/ftrace-direct-multi-modify.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c index 7a7822dfeb50..b03766c6217b 100644 --- a/samples/ftrace/ftrace-direct-multi-modify.c +++ b/samples/ftrace/ftrace-direct-multi-modify.c @@ -364,9 +364,15 @@ static int __init ftrace_direct_multi_init(void) ret = register_ftrace_direct(&direct, my_tramp); - if (!ret) - simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); - return ret; + if (ret) + return ret; + simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); + if (IS_ERR(simple_tsk)) { + unregister_ftrace_direct(&direct, my_tramp, true); + return PTR_ERR(simple_tsk); + } + + return 0; } static void __exit ftrace_direct_multi_exit(void) From 390f6bd8583d177029d9df4bea6667509e55a765 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= Date: Thu, 27 Aug 2026 18:43:22 +0000 Subject: [PATCH 08/10] tracing/user_events: Clear copied tracing state before fork duplication MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit dup_task_struct() copies user_event_mm from the parent into the child, without grabbing a reference to it. user_event_mm_dup() should replace it, but it leaves that copied pointer unmodified if user_event_mm_alloc() fails. When the child exits, user_event_mm_remove() decrements a reference the child never owned, which ultimately frees user_event_mm, while the parent still as a stale pointer to it. This creates a UAF, which KASAN reports as: BUG: KASAN: slab-use-after-free in current_user_event_mm+0x51/0x1d0 Write of size 4 at addr ffff888005010d30 by task init/44 Call Trace: kasan_report+0xce/0x100 kasan_check_range+0x10f/0x1e0 current_user_event_mm+0x51/0x1d0 user_events_ioctl+0x82e/0x15c0 __x64_sys_ioctl+0x139/0x1c0 do_syscall_64+0xce/0x450 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 44: __kasan_kmalloc+0x8f/0xa0 __kmalloc_cache_noprof+0x180/0x3a0 user_event_mm_alloc+0x3c/0x1f0 current_user_event_mm+0x88/0x1d0 Freed by task 42: __kasan_slab_free+0x43/0x70 kfree+0x13a/0x390 process_one_work+0x696/0xf90 worker_thread+0x420/0xba0 The fix simply clears the copied pointer before any possible failure. In case of failure, the child then has nothing to free. Cc: stable@vger.kernel.org Fixes: 7235759084a4 ("tracing/user_events: Use remote writes for event enablement") Link: https://patch.msgid.link/20260827184321.2964601-2-Jeremy.Jean@oss.cyber.gouv.fr Assisted-by: Codex:gpt-5 Signed-off-by: Jérémy Jean Reviewed-by: Bradley Morgan Signed-off-by: Steven Rostedt --- kernel/trace/trace_events_user.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index 2bbc89d4a266..93cda2f6f269 100644 --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -868,6 +868,9 @@ void user_event_mm_dup(struct task_struct *t, struct user_event_mm *old_mm) struct user_event_mm *mm = user_event_mm_alloc(t); struct user_event_enabler *enabler; + /* On failure, do not free parent's copy */ + t->user_event_mm = NULL; + if (!mm) return; From e0d3aed7b12cf37b74c7cc5265073d0263b49cde Mon Sep 17 00:00:00 2001 From: Ivan Immanuel Shaji Date: Tue, 25 Aug 2026 12:52:49 -0400 Subject: [PATCH 09/10] tracing: 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. The current !retry test reverses both outcomes. It returns an error after a successful final replacement, leaving the link update complete but the reader bookkeeping unfinished. After a failed final replacement, it falls through and updates the head and reader pointers as though the replacement succeeded, which can corrupt the ring. Treat only a negative counter as exhaustion and return the documented -EBUSY error. Cc: stable@vger.kernel.org Fixes: 34e5b958bdad ("tracing: Introduce simple_ring_buffer") Link: https://patch.msgid.link/20260825-kernel-patch-1-v2-1-bb3461807a32@gmail.com Assisted-by: LLM sparse Reviewed-by: Vincent Donnefort Signed-off-by: Ivan Immanuel Shaji Signed-off-by: Steven Rostedt --- kernel/trace/simple_ring_buffer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/trace/simple_ring_buffer.c b/kernel/trace/simple_ring_buffer.c index f4642f5adda3..49913bb0057a 100644 --- a/kernel/trace/simple_ring_buffer.c +++ b/kernel/trace/simple_ring_buffer.c @@ -160,8 +160,8 @@ int simple_ring_buffer_swap_reader_page(struct simple_rb_per_cpu *cpu_buffer) overrun = cpu_buffer->meta->overrun; } while (!simple_bpage_unset_head_link(last, reader, SIMPLE_RB_LINK_NORMAL) && retry--); - if (!retry) - return -EINVAL; + if (retry < 0) + return -EBUSY; cpu_buffer->head_page = simple_bpage_from_link(reader->link.next); cpu_buffer->head_page->link.prev = &reader->link; From 5eab74874d11160725c42ab676ba97a797a362eb Mon Sep 17 00:00:00 2001 From: Ivan Immanuel Shaji Date: Tue, 25 Aug 2026 12:52:50 -0400 Subject: [PATCH 10/10] ring-buffer: Stop remote reader update when page swap fails The remote swap_reader_page callback can return -EBUSY when the writer moves the head before the remote catches it, particularly during an event storm on a small buffer. __rb_get_reader_page_from_remote() currently warns about that failure but continues with the unchanged reader ID and rearranges the local page list as though the swap succeeded. Handle the callback failure as a recoverable error. Report it with pr_warn_ratelimited() and return NULL. Callers already handle a NULL reader page as a failed attempt. This avoids splicing the same page as both the previous and new reader without flooding the log under contention. Cc: stable@vger.kernel.org Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes") Link: https://patch.msgid.link/20260825-kernel-patch-1-v2-2-bb3461807a32@gmail.com Assisted-by: LLM sparse Signed-off-by: Ivan Immanuel Shaji Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 5fc009edc1ec..b7d076b6edcf 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5805,8 +5805,11 @@ __rb_get_reader_page_from_remote(struct ring_buffer_per_cpu *cpu_buffer) prev_reader = cpu_buffer->subbuf_ids[cpu_buffer->meta_page->reader.id]; - WARN_ON_ONCE(cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu, - cpu_buffer->remote->priv)); + if (cpu_buffer->remote->swap_reader_page(cpu_buffer->cpu, + cpu_buffer->remote->priv)) { + pr_warn_ratelimited("Remote reader page swap failed\n"); + return NULL; + } /* nr_pages doesn't include the reader page */ if (WARN_ON_ONCE(cpu_buffer->meta_page->reader.id > cpu_buffer->nr_pages)) return NULL;