linux-stable.git/kernel/trace/trace.c, branch v6.17.8

tracing: Stop fortify-string from warning in tracing_mark_raw_write()

2025-10-15T10:04:18+00:00

commit 54b91e54b113d4f15ab023a44f508251db6e22e7 upstream.

The way tracing_mark_raw_write() records its data is that it has the
following structure:

  struct {
	struct trace_entry;
	int id;
	char buf[];
  };

But memcpy(&entry->id, buf, size) triggers the following warning when the
size is greater than the id:

 ------------[ cut here ]------------
 memcpy: detected field-spanning write (size 6) of single field "&entry->id" at kernel/trace/trace.c:7458 (size 4)
 WARNING: CPU: 7 PID: 995 at kernel/trace/trace.c:7458 write_raw_marker_to_buffer.isra.0+0x1f9/0x2e0
 Modules linked in:
 CPU: 7 UID: 0 PID: 995 Comm: bash Not tainted 6.17.0-test-00007-g60b82183e78a-dirty #211 PREEMPT(voluntary)
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
 RIP: 0010:write_raw_marker_to_buffer.isra.0+0x1f9/0x2e0
 Code: 04 00 75 a7 b9 04 00 00 00 48 89 de 48 89 04 24 48 c7 c2 e0 b1 d1 b2 48 c7 c7 40 b2 d1 b2 c6 05 2d 88 6a 04 01 e8 f7 e8 bd ff <0f> 0b 48 8b 04 24 e9 76 ff ff ff 49 8d 7c 24 04 49 8d 5c 24 08 48
 RSP: 0018:ffff888104c3fc78 EFLAGS: 00010292
 RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 1ffffffff6b363b4 RDI: 0000000000000001
 RBP: ffff888100058a00 R08: ffffffffb041d459 R09: ffffed1020987f40
 R10: 0000000000000007 R11: 0000000000000001 R12: ffff888100bb9010
 R13: 0000000000000000 R14: 00000000000003e3 R15: ffff888134800000
 FS:  00007fa61d286740(0000) GS:ffff888286cad000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000560d28d509f1 CR3: 00000001047a4006 CR4: 0000000000172ef0
 Call Trace:
  
  tracing_mark_raw_write+0x1fe/0x290
  ? __pfx_tracing_mark_raw_write+0x10/0x10
  ? security_file_permission+0x50/0xf0
  ? rw_verify_area+0x6f/0x4b0
  vfs_write+0x1d8/0xdd0
  ? __pfx_vfs_write+0x10/0x10
  ? __pfx_css_rstat_updated+0x10/0x10
  ? count_memcg_events+0xd9/0x410
  ? fdget_pos+0x53/0x5e0
  ksys_write+0x182/0x200
  ? __pfx_ksys_write+0x10/0x10
  ? do_user_addr_fault+0x4af/0xa30
  do_syscall_64+0x63/0x350
  entry_SYSCALL_64_after_hwframe+0x76/0x7e
 RIP: 0033:0x7fa61d318687
 Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
 RSP: 002b:00007ffd87fe0120 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
 RAX: ffffffffffffffda RBX: 00007fa61d286740 RCX: 00007fa61d318687
 RDX: 0000000000000006 RSI: 0000560d28d509f0 RDI: 0000000000000001
 RBP: 0000560d28d509f0 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000006
 R13: 00007fa61d4715c0 R14: 00007fa61d46ee80 R15: 0000000000000000
  
 ---[ end trace 0000000000000000 ]---

This is because fortify string sees that the size of entry->id is only 4
bytes, but it is writing more than that. But this is OK as the
dynamic_array is allocated to handle that copy.

The size allocated on the ring buffer was actually a bit too big:

  size = sizeof(*entry) + cnt;

But cnt includes the 'id' and the buffer data, so adding cnt to the size
of *entry actually allocates too much on the ring buffer.

Change the allocation to:

  size = struct_size(entry, buf, cnt - sizeof(entry->id));

and the memcpy() to unsafe_memcpy() with an added justification.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Andrew Morton 
Link: https://lore.kernel.org/20251011112032.77be18e4@gandalf.local.home
Fixes: 64cf7d058a00 ("tracing: Have trace_marker use per-cpu data to read user space")
Reported-by: syzbot+9a2ede1643175f350105@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68e973f5.050a0220.1186a4.0010.GAE@google.com/
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Fix tracing_mark_raw_write() to use buf and not ubuf

2025-10-15T10:04:18+00:00

commit bda745ee8fbb63330d8f2f2ea4157229a5df959e upstream.

The fix to use a per CPU buffer to read user space tested only the writes
to trace_marker. But it appears that the selftests are missing tests to
the trace_maker_raw file. The trace_maker_raw file is used by applications
that writes data structures and not strings into the file, and the tools
read the raw ring buffer to process the structures it writes.

The fix that reads the per CPU buffers passes the new per CPU buffer to
the trace_marker file writes, but the update to the trace_marker_raw write
read the data from user space into the per CPU buffer, but then still used
then passed the user space address to the function that records the data.

Pass in the per CPU buffer and not the user space address.

TODO: Add a test to better test trace_marker_raw.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Cc: Andrew Morton 
Link: https://lore.kernel.org/20251011035243.386098147@kernel.org
Fixes: 64cf7d058a00 ("tracing: Have trace_marker use per-cpu data to read user space")
Reported-by: syzbot+9a2ede1643175f350105@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68e973f5.050a0220.1186a4.0010.GAE@google.com/
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Have trace_marker use per-cpu data to read user space

2025-10-15T10:04:17+00:00

commit 64cf7d058a005c5c31eb8a0b741f35dc12915d18 upstream.

It was reported that using __copy_from_user_inatomic() can actually
schedule. Which is bad when preemption is disabled. Even though there's
logic to check in_atomic() is set, but this is a nop when the kernel is
configured with PREEMPT_NONE. This is due to page faulting and the code
could schedule with preemption disabled.

Link: https://lore.kernel.org/all/20250819105152.2766363-1-luogengkun@huaweicloud.com/

The solution was to change the __copy_from_user_inatomic() to
copy_from_user_nofault(). But then it was reported that this caused a
regression in Android. There's several applications writing into
trace_marker() in Android, but now instead of showing the expected data,
it is showing:

  tracing_mark_write: 

After reverting the conversion to copy_from_user_nofault(), Android was
able to get the data again.

Writes to the trace_marker is a way to efficiently and quickly enter data
into the Linux tracing buffer. It takes no locks and was designed to be as
non-intrusive as possible. This means it cannot allocate memory, and must
use pre-allocated data.

A method that is actively being worked on to have faultable system call
tracepoints read user space data is to allocate per CPU buffers, and use
them in the callback. The method uses a technique similar to seqcount.
That is something like this:

	preempt_disable();
	cpu = smp_processor_id();
	buffer = this_cpu_ptr(&pre_allocated_cpu_buffers, cpu);
	do {
		cnt = nr_context_switches_cpu(cpu);
		migrate_disable();
		preempt_enable();
		ret = copy_from_user(buffer, ptr, size);
		preempt_disable();
		migrate_enable();
	} while (!ret && cnt != nr_context_switches_cpu(cpu));

	if (!ret)
		ring_buffer_write(buffer);
	preempt_enable();

It's a little more involved than that, but the above is the basic logic.
The idea is to acquire the current CPU buffer, disable migration, and then
enable preemption. At this moment, it can safely use copy_from_user().
After reading the data from user space, it disables preemption again. It
then checks to see if there was any new scheduling on this CPU. If there
was, it must assume that the buffer was corrupted by another task. If
there wasn't, then the buffer is still valid as only tasks in preemptable
context can write to this buffer and only those that are running on the
CPU.

By using this method, where trace_marker open allocates the per CPU
buffers, trace_marker writes can access user space and even fault it in,
without having to allocate or take any locks of its own.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Luo Gengkun 
Cc: Wattson CI 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/20251008124510.6dba541a@gandalf.local.home
Fixes: 3d62ab32df065 ("tracing: Fix tracing_marker may trigger page fault during preempt_disable")
Reported-by: Runping Lai 
Tested-by: Runping Lai 
Closes: https://lore.kernel.org/linux-trace-kernel/20251007003417.3470979-2-runpinglai@google.com/
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Silence warning when chunk allocation fails in trace_pid_write

2025-09-08T18:56:43+00:00

Syzkaller trigger a fault injection warning:

WARNING: CPU: 1 PID: 12326 at tracepoint_add_func+0xbfc/0xeb0
Modules linked in:
CPU: 1 UID: 0 PID: 12326 Comm: syz.6.10325 Tainted: G U 6.14.0-rc5-syzkaller #0
Tainted: [U]=USER
Hardware name: Google Compute Engine/Google Compute Engine
RIP: 0010:tracepoint_add_func+0xbfc/0xeb0 kernel/tracepoint.c:294
Code: 09 fe ff 90 0f 0b 90 0f b6 74 24 43 31 ff 41 bc ea ff ff ff
RSP: 0018:ffffc9000414fb48 EFLAGS: 00010283
RAX: 00000000000012a1 RBX: ffffffff8e240ae0 RCX: ffffc90014b78000
RDX: 0000000000080000 RSI: ffffffff81bbd78b RDI: 0000000000000001
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffffffffffffffef
R13: 0000000000000000 R14: dffffc0000000000 R15: ffffffff81c264f0
FS:  00007f27217f66c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e80dff8 CR3: 00000000268f8000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 
 tracepoint_probe_register_prio+0xc0/0x110 kernel/tracepoint.c:464
 register_trace_prio_sched_switch include/trace/events/sched.h:222 [inline]
 register_pid_events kernel/trace/trace_events.c:2354 [inline]
 event_pid_write.isra.0+0x439/0x7a0 kernel/trace/trace_events.c:2425
 vfs_write+0x24c/0x1150 fs/read_write.c:677
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

We can reproduce the warning by following the steps below:
1. echo 8 >> set_event_notrace_pid. Let tr->filtered_pids owns one pid
   and register sched_switch tracepoint.
2. echo ' ' >> set_event_pid, and perform fault injection during chunk
   allocation of trace_pid_list_alloc. Let pid_list with no pid and
assign to tr->filtered_pids.
3. echo ' ' >> set_event_pid. Let pid_list is NULL and assign to
   tr->filtered_pids.
4. echo 9 >> set_event_pid, will trigger the double register
   sched_switch tracepoint warning.

The reason is that syzkaller injects a fault into the chunk allocation
in trace_pid_list_alloc, causing a failure in trace_pid_list_set, which
may trigger double register of the same tracepoint. This only occurs
when the system is about to crash, but to suppress this warning, let's
add failure handling logic to trace_pid_list_set.

Link: https://lore.kernel.org/20250908024658.2390398-1-pulehui@huaweicloud.com
Fixes: 8d6e90983ade ("tracing: Create a sparse bitmask for pid filtering")
Reported-by: syzbot+161412ccaeff20ce4dde@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67cb890e.050a0220.d8275.022e.GAE@google.com
Signed-off-by: Pu Lehui 
Signed-off-by: Steven Rostedt (Google)

tracing: Fix tracing_marker may trigger page fault during preempt_disable

2025-09-02T16:02:42+00:00

Both tracing_mark_write and tracing_mark_raw_write call
__copy_from_user_inatomic during preempt_disable. But in some case,
__copy_from_user_inatomic may trigger page fault, and will call schedule()
subtly. And if a task is migrated to other cpu, the following warning will
be trigger:
        if (RB_WARN_ON(cpu_buffer,
                       !local_read(&cpu_buffer->committing)))

An example can illustrate this issue:

process flow						CPU
---------------------------------------------------------------------

tracing_mark_raw_write():				cpu:0
   ...
   ring_buffer_lock_reserve():				cpu:0
      ...
      cpu = raw_smp_processor_id()			cpu:0
      cpu_buffer = buffer->buffers[cpu]			cpu:0
      ...
   ...
   __copy_from_user_inatomic():				cpu:0
      ...
      # page fault
      do_mem_abort():					cpu:0
         ...
         # Call schedule
         schedule()					cpu:0
	 ...
   # the task schedule to cpu1
   __buffer_unlock_commit():				cpu:1
      ...
      ring_buffer_unlock_commit():			cpu:1
	 ...
	 cpu = raw_smp_processor_id()			cpu:1
	 cpu_buffer = buffer->buffers[cpu]		cpu:1

As shown above, the process will acquire cpuid twice and the return values
are not the same.

To fix this problem using copy_from_user_nofault instead of
__copy_from_user_inatomic, as the former performs 'access_ok' before
copying.

Link: https://lore.kernel.org/20250819105152.2766363-1-luogengkun@huaweicloud.com
Fixes: 656c7f0d2d2b ("tracing: Replace kmap with copy_from_user() in trace_marker writing")
Signed-off-by: Luo Gengkun 
Reviewed-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google)

ftrace: Fix potential warning in trace_printk_seq during ftrace_dump

2025-08-22T21:32:36+00:00

When calling ftrace_dump_one() concurrently with reading trace_pipe,
a WARN_ON_ONCE() in trace_printk_seq() can be triggered due to a race
condition.

The issue occurs because:

CPU0 (ftrace_dump)                              CPU1 (reader)
echo z > /proc/sysrq-trigger

!trace_empty(&iter)
trace_iterator_reset(&iter) <- len = size = 0
                                                cat /sys/kernel/tracing/trace_pipe
trace_find_next_entry_inc(&iter)
  __find_next_entry
    ring_buffer_empty_cpu <- all empty
  return NULL

trace_printk_seq(&iter.seq)
  WARN_ON_ONCE(s->seq.len >= s->seq.size)

In the context between trace_empty() and trace_find_next_entry_inc()
during ftrace_dump, the ring buffer data was consumed by other readers.
This caused trace_find_next_entry_inc to return NULL, failing to populate
`iter.seq`. At this point, due to the prior trace_iterator_reset, both
`iter.seq.len` and `iter.seq.size` were set to 0. Since they are equal,
the WARN_ON_ONCE condition is triggered.

Move the trace_printk_seq() into the if block that checks to make sure the
return value of trace_find_next_entry_inc() is non-NULL in
ftrace_dump_one(), ensuring the 'iter.seq' is properly populated before
subsequent operations.

Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Cc: Ingo Molnar 
Link: https://lore.kernel.org/20250822033343.3000289-1-wutengda@huaweicloud.com
Fixes: d769041f8653 ("ring_buffer: implement new locking")
Signed-off-by: Tengda Wu 
Signed-off-by: Steven Rostedt (Google)

tracing: Limit access to parser->buffer when trace_get_user failed

2025-08-20T13:20:30+00:00

When the length of the string written to set_ftrace_filter exceeds
FTRACE_BUFF_MAX, the following KASAN alarm will be triggered:

BUG: KASAN: slab-out-of-bounds in strsep+0x18c/0x1b0
Read of size 1 at addr ffff0000d00bd5ba by task ash/165

CPU: 1 UID: 0 PID: 165 Comm: ash Not tainted 6.16.0-g6bcdbd62bd56-dirty
Hardware name: linux,dummy-virt (DT)
Call trace:
 show_stack+0x34/0x50 (C)
 dump_stack_lvl+0xa0/0x158
 print_address_description.constprop.0+0x88/0x398
 print_report+0xb0/0x280
 kasan_report+0xa4/0xf0
 __asan_report_load1_noabort+0x20/0x30
 strsep+0x18c/0x1b0
 ftrace_process_regex.isra.0+0x100/0x2d8
 ftrace_regex_release+0x484/0x618
 __fput+0x364/0xa58
 ____fput+0x28/0x40
 task_work_run+0x154/0x278
 do_notify_resume+0x1f0/0x220
 el0_svc+0xec/0xf0
 el0t_64_sync_handler+0xa0/0xe8
 el0t_64_sync+0x1ac/0x1b0

The reason is that trace_get_user will fail when processing a string
longer than FTRACE_BUFF_MAX, but not set the end of parser->buffer to 0.
Then an OOB access will be triggered in ftrace_regex_release->
ftrace_process_regex->strsep->strpbrk. We can solve this problem by
limiting access to parser->buffer when trace_get_user failed.

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/20250813040232.1344527-1-pulehui@huaweicloud.com
Fixes: 8c9af478c06b ("ftrace: Handle commands when closing set_ftrace_filter file")
Signed-off-by: Pu Lehui 
Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-v6.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2025-08-03T22:03:04+00:00

Pull more tracing updates from Steven Rostedt:

 - Remove unneeded goto out statements

   Over time, the logic was restructured but left a "goto out" where the
   out label simply did a "return ret;". Instead of jumping to this out
   label, simply return immediately and remove the out label.

 - Add guard(ring_buffer_nest)

   Some calls to the tracing ring buffer can happen when the ring buffer
   is already being written to at the same context (for example, a
   trace_printk() in between a ring_buffer_lock_reserve() and a
   ring_buffer_unlock_commit()).

   In order to not trigger the recursion detection, these functions use
   ring_buffer_nest_start() and ring_buffer_nest_end(). Create a guard()
   for these functions so that their use cases can be simplified and not
   need to use goto for the release.

 - Clean up the tracing code with guard() and __free() logic

   There were several locations that were prime candidates for using
   guard() and __free() helpers. Switch them over to use them.

 - Fix output of function argument traces for unsigned int values

   The function tracer with "func-args" option set will record up to 6
   argument registers and then use BTF to format them for human
   consumption when the trace file is read. There are several arguments
   that are "unsigned long" and even "unsigned int" that are either and
   address or a mask. It is easier to understand if they were printed
   using hexadecimal instead of decimal. The old method just printed all
   non-pointer values as signed integers, which made it even worse for
   unsigned integers.

   For instance, instead of:

     __local_bh_disable_ip(ip=-2127311112, cnt=256) <-handle_softirqs

   show:

     __local_bh_disable_ip(ip=0xffffffff8133cef8, cnt=0x100) <-handle_softirqs"

* tag 'trace-v6.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: Have unsigned int function args displayed as hexadecimal
  ring-buffer: Convert ring_buffer_write() to use guard(preempt_notrace)
  tracing: Use __free(kfree) in trace.c to remove gotos
  tracing: Add guard() around locks and mutexes in trace.c
  tracing: Add guard(ring_buffer_nest)
  tracing: Remove unneeded goto out logic

Merge tag 'modules-6.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/modules/linux

2025-08-03T21:16:52+00:00

Pull module updates from Daniel Gomez:
 "This is a small set of changes for modules, primarily to extend module
  users to use the module data structures in combination with the
  already no-op stub module functions, even when support for modules is
  disabled in the kernel configuration. This change follows the kernel's
  coding style for conditional compilation and allows kunit code to drop
  all CONFIG_MODULES ifdefs, which is also part of the changes. This
  should allow others part of the kernel to do the same cleanup.

  The remaining changes include a fix for module name length handling
  which could potentially lead to the removal of an incorrect module,
  and various cleanups"

* tag 'modules-6.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/modules/linux:
  module: Rename MAX_PARAM_PREFIX_LEN to __MODULE_NAME_LEN
  tracing: Replace MAX_PARAM_PREFIX_LEN with MODULE_NAME_LEN
  module: Restore the moduleparam prefix length check
  module: Remove unnecessary +1 from last_unloaded_module::name size
  module: Prevent silent truncation of module name in delete_module(2)
  kunit: test: Drop CONFIG_MODULE ifdeffery
  module: make structure definitions always visible
  module: move 'struct module_use' to internal.h

tracing: Use __free(kfree) in trace.c to remove gotos

2025-08-01T20:49:15+00:00

There's a couple of locations that have goto out in trace.c for the only
purpose of freeing a variable that was allocated. These can be replaced
with __free(kfree).

Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Cc: Andrew Morton 
Link: https://lore.kernel.org/20250801203858.040892777@kernel.org
Signed-off-by: Steven Rostedt (Google)