linux-stable.git/kernel/trace/trace.c, branch v6.13.9

tracing: Fix using ret variable in tracing_set_tracer()

2025-02-27T12:34:22+00:00

commit 22bec11a569983f39c6061cb82279e7de9e3bdfc upstream.

When the function tracing_set_tracer() switched over to using the guard()
infrastructure, it did not need to save the 'ret' variable and would just
return the value when an error arised, instead of setting ret and jumping
to an out label.

When CONFIG_TRACER_SNAPSHOT is enabled, it had code that expected the
"ret" variable to be initialized to zero and had set 'ret' while holding
an arch_spin_lock() (not used by guard), and then upon releasing the lock
it would check 'ret' and exit if set. But because ret was only set when an
error occurred while holding the locks, 'ret' would be used uninitialized
if there was no error. The code in the CONFIG_TRACER_SNAPSHOT block should
be self contain. Make sure 'ret' is also set when no error occurred.

Cc: Mathieu Desnoyers 
Link: https://lore.kernel.org/20250106111143.2f90ff65@gandalf.local.home
Reported-by: kernel test robot 
Reported-by: Dan Carpenter 
Closes: https://lore.kernel.org/r/202412271654.nJVBuwmF-lkp@intel.com/
Fixes: d33b10c0c73ad ("tracing: Switch trace.c code over to use guard()")
Signed-off-by: Steven Rostedt (Google) 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Have the error of __tracing_resize_ring_buffer() passed to user

2025-02-27T12:34:13+00:00

[ Upstream commit 60b8f711143de7cd9c0f55be0fe7eb94b19eb5c7 ]

Currently if __tracing_resize_ring_buffer() returns an error, the
tracing_resize_ringbuffer() returns -ENOMEM. But it may not be a memory
issue that caused the function to fail. If the ring buffer is memory
mapped, then the resizing of the ring buffer will be disabled. But if the
user tries to resize the buffer, it will get an -ENOMEM returned, which is
confusing because there is plenty of memory. The actual error returned was
-EBUSY, which would make much more sense to the user.

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers 
Cc: Vincent Donnefort 
Link: https://lore.kernel.org/20250213134132.7e4505d7@gandalf.local.home
Fixes: 117c39200d9d7 ("ring-buffer: Introducing ring-buffer mapping functions")
Signed-off-by: Steven Rostedt (Google) 
Reviewed-by: Masami Hiramatsu (Google) 
Signed-off-by: Sasha Levin

tracing: Switch trace.c code over to use guard()

2025-02-27T12:34:13+00:00

[ Upstream commit d33b10c0c73adca00f72bf4a153a07b7f5f34715 ]

There are several functions in trace.c that have "goto out;" or
equivalent on error in order to release locks or free values that were
allocated. This can be error prone or just simply make the code more
complex.

Switch every location that ends with unlocking a mutex or freeing on error
over to using the guard(mutex)() and __free() infrastructure to let the
compiler worry about releasing locks. This makes the code easier to read
and understand.

There's one place that should probably return an error but instead return
0. This does not change the return as the only changes are to do the
conversion without changing the logic. Fixing that location will have to
come later.

Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Cc: Peter Zijlstra 
Cc: Andrew Morton 
Acked-by: Masami Hiramatsu (Google) 
Link: https://lore.kernel.org/20241224221413.7b8c68c3@batman.local.home
Signed-off-by: Steven Rostedt (Google) 
Stable-dep-of: 60b8f711143d ("tracing: Have the error of __tracing_resize_ring_buffer() passed to user")
Signed-off-by: Sasha Levin

tracing: Do not allow mmap() of persistent ring buffer

2025-02-21T13:11:00+00:00

commit 129fe718819cc5e24ea2f489db9ccd4371f0c6f6 upstream.

When trying to mmap a trace instance buffer that is attached to
reserve_mem, it would crash:

 BUG: unable to handle page fault for address: ffffe97bd00025c8
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 2862f3067 P4D 2862f3067 PUD 0
 Oops: Oops: 0000 [#1] PREEMPT_RT SMP PTI
 CPU: 4 UID: 0 PID: 981 Comm: mmap-rb Not tainted 6.14.0-rc2-test-00003-g7f1a5e3fbf9e-dirty #233
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
 RIP: 0010:validate_page_before_insert+0x5/0xb0
 Code: e2 01 89 d0 c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 <48> 8b 46 08 a8 01 75 67 66 90 48 89 f0 8b 50 34 85 d2 74 76 48 89
 RSP: 0018:ffffb148c2f3f968 EFLAGS: 00010246
 RAX: ffff9fa5d3322000 RBX: ffff9fa5ccff9c08 RCX: 00000000b879ed29
 RDX: ffffe97bd00025c0 RSI: ffffe97bd00025c0 RDI: ffff9fa5ccff9c08
 RBP: ffffb148c2f3f9f0 R08: 0000000000000004 R09: 0000000000000004
 R10: 0000000000000000 R11: 0000000000000200 R12: 0000000000000000
 R13: 00007f16a18d5000 R14: ffff9fa5c48db6a8 R15: 0000000000000000
 FS:  00007f16a1b54740(0000) GS:ffff9fa73df00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: ffffe97bd00025c8 CR3: 00000001048c6006 CR4: 0000000000172ef0
 Call Trace:
  
  ? __die_body.cold+0x19/0x1f
  ? __die+0x2e/0x40
  ? page_fault_oops+0x157/0x2b0
  ? search_module_extables+0x53/0x80
  ? validate_page_before_insert+0x5/0xb0
  ? kernelmode_fixup_or_oops.isra.0+0x5f/0x70
  ? __bad_area_nosemaphore+0x16e/0x1b0
  ? bad_area_nosemaphore+0x16/0x20
  ? do_kern_addr_fault+0x77/0x90
  ? exc_page_fault+0x22b/0x230
  ? asm_exc_page_fault+0x2b/0x30
  ? validate_page_before_insert+0x5/0xb0
  ? vm_insert_pages+0x151/0x400
  __rb_map_vma+0x21f/0x3f0
  ring_buffer_map+0x21b/0x2f0
  tracing_buffers_mmap+0x70/0xd0
  __mmap_region+0x6f0/0xbd0
  mmap_region+0x7f/0x130
  do_mmap+0x475/0x610
  vm_mmap_pgoff+0xf2/0x1d0
  ksys_mmap_pgoff+0x166/0x200
  __x64_sys_mmap+0x37/0x50
  x64_sys_call+0x1670/0x1d70
  do_syscall_64+0xbb/0x1d0
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

The reason was that the code that maps the ring buffer pages to user space
has:

	page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);

And uses that in:

	vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);

But virt_to_page() does not work with vmap()'d memory which is what the
persistent ring buffer has. It is rather trivial to allow this, but for
now just disable mmap() of instances that have their ring buffer from the
reserve_mem option.

If an mmap() is performed on a persistent buffer it will return -ENODEV
just like it would if the .mmap field wasn't defined in the
file_operations structure.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Vincent Donnefort 
Link: https://lore.kernel.org/20250214115547.0d7287d3@gandalf.local.home
Fixes: 9b7bdf6f6ece6 ("tracing: Have trace_printk not use binary prints if boot buffer")
Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Greg Kroah-Hartman

tracing: Print lazy preemption model

2025-01-14T14:44:33+00:00

Print lazy preemption model in ftrace header when latency-format=1.

 # cat /sys/kernel/debug/sched/preempt
 none voluntary full (lazy)

Without patch:
  latency: 0 us, #232946/232946, CPU#40 | (M:unknown VP:0, KP:0, SP:0 HP:0 #P:80)
                                             ^^^^^^^

With Patch:
  latency: 0 us, #1897938/25566788, CPU#16 | (M:lazy VP:0, KP:0, SP:0 HP:0 #P:80)
                                                ^^^^

Now that lazy preemption is part of the kernel, make sure the tracing
infrastructure reflects that.

Link: https://lore.kernel.org/20250103093647.575919-1-sshegde@linux.ibm.com
Signed-off-by: Shrikanth Hegde 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google)

tracing: Prevent bad count for tracing_cpumask_write

2024-12-24T02:59:15+00:00

If a large count is provided, it will trigger a warning in bitmap_parse_user.
Also check zero for it.

Cc: stable@vger.kernel.org
Fixes: 9e01c1b74c953 ("cpumask: convert kernel trace functions")
Link: https://lore.kernel.org/20241216073238.2573704-1-lizhi.xu@windriver.com
Reported-by: syzbot+0aecfd34fb878546f3fd@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0aecfd34fb878546f3fd
Tested-by: syzbot+0aecfd34fb878546f3fd@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu 
Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-ringbuffer-v6.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2024-12-20T18:13:26+00:00

Pull ring-buffer fixes from Steven Rostedt:

 - Fix possible overflow of mmapped ring buffer with bad offset

   If the mmap() to the ring buffer passes in a start address that is
   passed the end of the mmapped file, it is not caught and a
   slab-out-of-bounds is triggered.

   Add a check to make sure the start address is within the bounds

 - Do not use TP_printk() to boot mapped ring buffers

   As a boot mapped ring buffer's data may have pointers that map to the
   previous boot's memory map, it is unsafe to allow the TP_printk() to
   be used to read the boot mapped buffer's events. If a TP_printk()
   points to a static string from within the kernel it will not match
   the current kernel mapping if KASLR is active, and it can fault.

   Have it simply print out the raw fields.

* tag 'trace-ringbuffer-v6.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  trace/ring-buffer: Do not use TP_printk() formatting for boot mapped buffers
  ring-buffer: Fix overflow in __rb_map_vma

trace/ring-buffer: Do not use TP_printk() formatting for boot mapped buffers

2024-12-18T19:20:38+00:00

The TP_printk() of a TRACE_EVENT() is a generic printf format that any
developer can create for their event. It may include pointers to strings
and such. A boot mapped buffer may contain data from a previous kernel
where the strings addresses are different.

One solution is to copy the event content and update the pointers by the
recorded delta, but a simpler solution (for now) is to just use the
print_fields() function to print these events. The print_fields() function
just iterates the fields and prints them according to what type they are,
and ignores the TP_printk() format from the event itself.

To understand the difference, when printing via TP_printk() the output
looks like this:

  4582.696626: kmem_cache_alloc: call_site=getname_flags+0x47/0x1f0 ptr=00000000e70e10e0 bytes_req=4096 bytes_alloc=4096 gfp_flags=GFP_KERNEL node=-1 accounted=false
  4582.696629: kmem_cache_alloc: call_site=alloc_empty_file+0x6b/0x110 ptr=0000000095808002 bytes_req=360 bytes_alloc=384 gfp_flags=GFP_KERNEL node=-1 accounted=false
  4582.696630: kmem_cache_alloc: call_site=security_file_alloc+0x24/0x100 ptr=00000000576339c3 bytes_req=16 bytes_alloc=16 gfp_flags=GFP_KERNEL|__GFP_ZERO node=-1 accounted=false
  4582.696653: kmem_cache_free: call_site=do_sys_openat2+0xa7/0xd0 ptr=00000000e70e10e0 name=names_cache

But when printing via print_fields() (echo 1 > /sys/kernel/tracing/options/fields)
the same event output looks like this:

  4582.696626: kmem_cache_alloc: call_site=0xffffffff92d10d97 (-1831793257) ptr=0xffff9e0e8571e000 (-107689771147264) bytes_req=0x1000 (4096) bytes_alloc=0x1000 (4096) gfp_flags=0xcc0 (3264) node=0xffffffff (-1) accounted=(0)
  4582.696629: kmem_cache_alloc: call_site=0xffffffff92d0250b (-1831852789) ptr=0xffff9e0e8577f800 (-107689770747904) bytes_req=0x168 (360) bytes_alloc=0x180 (384) gfp_flags=0xcc0 (3264) node=0xffffffff (-1) accounted=(0)
  4582.696630: kmem_cache_alloc: call_site=0xffffffff92efca74 (-1829778828) ptr=0xffff9e0e8d35d3b0 (-107689640864848) bytes_req=0x10 (16) bytes_alloc=0x10 (16) gfp_flags=0xdc0 (3520) node=0xffffffff (-1) accounted=(0)
  4582.696653: kmem_cache_free: call_site=0xffffffff92cfbea7 (-1831879001) ptr=0xffff9e0e8571e000 (-107689771147264) name=names_cache

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/20241218141507.28389a1d@gandalf.local.home
Fixes: 07714b4bb3f98 ("tracing: Handle old buffer mappings for event strings and functions")
Signed-off-by: Steven Rostedt (Google)

tracing: Check "%s" dereference via the field and not the TP_printk format

2024-12-17T16:40:11+00:00

The TP_printk() portion of a trace event is executed at the time a event
is read from the trace. This can happen seconds, minutes, hours, days,
months, years possibly later since the event was recorded. If the print
format contains a dereference to a string via "%s", and that string was
allocated, there's a chance that string could be freed before it is read
by the trace file.

To protect against such bugs, there are two functions that verify the
event. The first one is test_event_printk(), which is called when the
event is created. It reads the TP_printk() format as well as its arguments
to make sure nothing may be dereferencing a pointer that was not copied
into the ring buffer along with the event. If it is, it will trigger a
WARN_ON().

For strings that use "%s", it is not so easy. The string may not reside in
the ring buffer but may still be valid. Strings that are static and part
of the kernel proper which will not be freed for the life of the running
system, are safe to dereference. But to know if it is a pointer to a
static string or to something on the heap can not be determined until the
event is triggered.

This brings us to the second function that tests for the bad dereferencing
of strings, trace_check_vprintf(). It would walk through the printf format
looking for "%s", and when it finds it, it would validate that the pointer
is safe to read. If not, it would produces a WARN_ON() as well and write
into the ring buffer "[UNSAFE-MEMORY]".

The problem with this is how it used va_list to have vsnprintf() handle
all the cases that it didn't need to check. Instead of re-implementing
vsnprintf(), it would make a copy of the format up to the %s part, and
call vsnprintf() with the current va_list ap variable, where the ap would
then be ready to point at the string in question.

For architectures that passed va_list by reference this was possible. For
architectures that passed it by copy it was not. A test_can_verify()
function was used to differentiate between the two, and if it wasn't
possible, it would disable it.

Even for architectures where this was feasible, it was a stretch to rely
on such a method that is undocumented, and could cause issues later on
with new optimizations of the compiler.

Instead, the first function test_event_printk() was updated to look at
"%s" as well. If the "%s" argument is a pointer outside the event in the
ring buffer, it would find the field type of the event that is the problem
and mark the structure with a new flag called "needs_test". The event
itself will be marked by TRACE_EVENT_FL_TEST_STR to let it be known that
this event has a field that needs to be verified before the event can be
printed using the printf format.

When the event fields are created from the field type structure, the
fields would copy the field type's "needs_test" value.

Finally, before being printed, a new function ignore_event() is called
which will check if the event has the TEST_STR flag set (if not, it
returns false). If the flag is set, it then iterates through the events
fields looking for the ones that have the "needs_test" flag set.

Then it uses the offset field from the field structure to find the pointer
in the ring buffer event. It runs the tests to make sure that pointer is
safe to print and if not, it triggers the WARN_ON() and also adds to the
trace output that the event in question has an unsafe memory access.

The ignore_event() makes the trace_check_vprintf() obsolete so it is
removed.

Link: https://lore.kernel.org/all/CAHk-=wh3uOnqnZPpR0PeLZZtyWbZLboZ7cHLCKRWsocvs9Y7hQ@mail.gmail.com/

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Mark Rutland 
Cc: Mathieu Desnoyers 
Cc: Andrew Morton 
Cc: Al Viro 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/20241217024720.848621576@goodmis.org
Fixes: 5013f454a352c ("tracing: Add check of trace event print fmts for dereferencing pointers")
Signed-off-by: Steven Rostedt (Google)

tracing: Record task flag NEED_RESCHED_LAZY.

2024-11-22T22:49:39+00:00

The scheduler added NEED_RESCHED_LAZY scheduling. Record this state as
part of trace flags and expose it in the need_resched field.

Record and expose NEED_RESCHED_LAZY.

[bigeasy: Commit description, documentation bits.]

Cc: Peter Zijlstra 
Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Link: https://lore.kernel.org/20241122202849.7DfYpJR0@linutronix.de
Reviewed-by: Ankur Arora 
Reviewed-by: Steven Rostedt (Google) 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (Google)