linux.git/kernel/trace, branch v5.10.195 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git tracing: Zero the pipe cpumask on alloc to avoid spurious -EBUSY 2023-09-19T10:20:23+00:00 Brian Foster bfoster@redhat.com 2023-08-31T12:55:00+00:00 5103216b863fba74364c014cd2f77b0a837e808b commit 3d07fa1dd19035eb0b13ae6697efd5caa9033e74 upstream. The pipe cpumask used to serialize opens between the main and percpu trace pipes is not zeroed or initialized. This can result in spurious -EBUSY returns if underlying memory is not fully zeroed. This has been observed by immediate failure to read the main trace_pipe file on an otherwise newly booted and idle system: # cat /sys/kernel/debug/tracing/trace_pipe cat: /sys/kernel/debug/tracing/trace_pipe: Device or resource busy Zero the allocation of pipe_cpumask to avoid the problem. Link: https://lore.kernel.org/linux-trace-kernel/20230831125500.986862-1-bfoster@redhat.com Cc: stable@vger.kernel.org Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes") Reviewed-by: Zheng Yejian <zhengyejian1@huawei.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 3d07fa1dd19035eb0b13ae6697efd5caa9033e74 upstream.

The pipe cpumask used to serialize opens between the main and percpu
trace pipes is not zeroed or initialized. This can result in
spurious -EBUSY returns if underlying memory is not fully zeroed.
This has been observed by immediate failure to read the main
trace_pipe file on an otherwise newly booted and idle system:

 # cat /sys/kernel/debug/tracing/trace_pipe
 cat: /sys/kernel/debug/tracing/trace_pipe: Device or resource busy

Zero the allocation of pipe_cpumask to avoid the problem.

Link: https://lore.kernel.org/linux-trace-kernel/20230831125500.986862-1-bfoster@redhat.com

Cc: stable@vger.kernel.org
Fixes: c2489bb7e6be ("tracing: Introduce pipe_cpumask to avoid race on trace_pipes")
Reviewed-by: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tracing: Fix race issue between cpu buffer write and swap 2023-09-19T10:20:19+00:00 Zheng Yejian zhengyejian1@huawei.com 2023-08-31T13:27:39+00:00 c5d30d6aa83d99fba8dfdd9cf6c4e4e7a63244db [ Upstream commit 3163f635b20e9e1fb4659e74f47918c9dddfe64e ] Warning happened in rb_end_commit() at code: if (RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing))) WARNING: CPU: 0 PID: 139 at kernel/trace/ring_buffer.c:3142 rb_commit+0x402/0x4a0 Call Trace: ring_buffer_unlock_commit+0x42/0x250 trace_buffer_unlock_commit_regs+0x3b/0x250 trace_event_buffer_commit+0xe5/0x440 trace_event_buffer_reserve+0x11c/0x150 trace_event_raw_event_sched_switch+0x23c/0x2c0 __traceiter_sched_switch+0x59/0x80 __schedule+0x72b/0x1580 schedule+0x92/0x120 worker_thread+0xa0/0x6f0 It is because the race between writing event into cpu buffer and swapping cpu buffer through file per_cpu/cpu0/snapshot: Write on CPU 0 Swap buffer by per_cpu/cpu0/snapshot on CPU 1 -------- -------- tracing_snapshot_write() [...] ring_buffer_lock_reserve() cpu_buffer = buffer->buffers[cpu]; // 1. Suppose find 'cpu_buffer_a'; [...] rb_reserve_next_event() [...] ring_buffer_swap_cpu() if (local_read(&cpu_buffer_a->committing)) goto out_dec; if (local_read(&cpu_buffer_b->committing)) goto out_dec; buffer_a->buffers[cpu] = cpu_buffer_b; buffer_b->buffers[cpu] = cpu_buffer_a; // 2. cpu_buffer has swapped here. rb_start_commit(cpu_buffer); if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { // 3. This check passed due to 'cpu_buffer->buffer' [...] // has not changed here. return NULL; } cpu_buffer_b->buffer = buffer_a; cpu_buffer_a->buffer = buffer_b; [...] // 4. Reserve event from 'cpu_buffer_a'. ring_buffer_unlock_commit() [...] cpu_buffer = buffer->buffers[cpu]; // 5. Now find 'cpu_buffer_b' !!! rb_commit(cpu_buffer) rb_end_commit() // 6. WARN for the wrong 'committing' state !!! Based on above analysis, we can easily reproduce by following testcase: ``` bash #!/bin/bash dmesg -n 7 sysctl -w kernel.panic_on_warn=1 TR=/sys/kernel/tracing echo 7 > ${TR}/buffer_size_kb echo "sched:sched_switch" > ${TR}/set_event while [ true ]; do echo 1 > ${TR}/per_cpu/cpu0/snapshot done & while [ true ]; do echo 1 > ${TR}/per_cpu/cpu0/snapshot done & while [ true ]; do echo 1 > ${TR}/per_cpu/cpu0/snapshot done & ``` To fix it, IIUC, we can use smp_call_function_single() to do the swap on the target cpu where the buffer is located, so that above race would be avoided. Link: https://lore.kernel.org/linux-trace-kernel/20230831132739.4070878-1-zhengyejian1@huawei.com Cc: <mhiramat@kernel.org> Fixes: f1affcaaa861 ("tracing: Add snapshot in the per_cpu trace directories") Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 3163f635b20e9e1fb4659e74f47918c9dddfe64e ]

Warning happened in rb_end_commit() at code:
	if (RB_WARN_ON(cpu_buffer, !local_read(&cpu_buffer->committing)))

  WARNING: CPU: 0 PID: 139 at kernel/trace/ring_buffer.c:3142
	rb_commit+0x402/0x4a0
  Call Trace:
   ring_buffer_unlock_commit+0x42/0x250
   trace_buffer_unlock_commit_regs+0x3b/0x250
   trace_event_buffer_commit+0xe5/0x440
   trace_event_buffer_reserve+0x11c/0x150
   trace_event_raw_event_sched_switch+0x23c/0x2c0
   __traceiter_sched_switch+0x59/0x80
   __schedule+0x72b/0x1580
   schedule+0x92/0x120
   worker_thread+0xa0/0x6f0

It is because the race between writing event into cpu buffer and swapping
cpu buffer through file per_cpu/cpu0/snapshot:

  Write on CPU 0             Swap buffer by per_cpu/cpu0/snapshot on CPU 1
  --------                   --------
                             tracing_snapshot_write()
                               [...]

  ring_buffer_lock_reserve()
    cpu_buffer = buffer->buffers[cpu]; // 1. Suppose find 'cpu_buffer_a';
    [...]
    rb_reserve_next_event()
      [...]

                               ring_buffer_swap_cpu()
                                 if (local_read(&cpu_buffer_a->committing))
                                     goto out_dec;
                                 if (local_read(&cpu_buffer_b->committing))
                                     goto out_dec;
                                 buffer_a->buffers[cpu] = cpu_buffer_b;
                                 buffer_b->buffers[cpu] = cpu_buffer_a;
                                 // 2. cpu_buffer has swapped here.

      rb_start_commit(cpu_buffer);
      if (unlikely(READ_ONCE(cpu_buffer->buffer)
          != buffer)) { // 3. This check passed due to 'cpu_buffer->buffer'
        [...]           //    has not changed here.
        return NULL;
      }
                                 cpu_buffer_b->buffer = buffer_a;
                                 cpu_buffer_a->buffer = buffer_b;
                                 [...]

      // 4. Reserve event from 'cpu_buffer_a'.

  ring_buffer_unlock_commit()
    [...]
    cpu_buffer = buffer->buffers[cpu]; // 5. Now find 'cpu_buffer_b' !!!
    rb_commit(cpu_buffer)
      rb_end_commit()  // 6. WARN for the wrong 'committing' state !!!

Based on above analysis, we can easily reproduce by following testcase:
  ``` bash
  #!/bin/bash

  dmesg -n 7
  sysctl -w kernel.panic_on_warn=1
  TR=/sys/kernel/tracing
  echo 7 > ${TR}/buffer_size_kb
  echo "sched:sched_switch" > ${TR}/set_event
  while [ true ]; do
          echo 1 > ${TR}/per_cpu/cpu0/snapshot
  done &
  while [ true ]; do
          echo 1 > ${TR}/per_cpu/cpu0/snapshot
  done &
  while [ true ]; do
          echo 1 > ${TR}/per_cpu/cpu0/snapshot
  done &
  ```

To fix it, IIUC, we can use smp_call_function_single() to do the swap on
the target cpu where the buffer is located, so that above race would be
avoided.

Link: https://lore.kernel.org/linux-trace-kernel/20230831132739.4070878-1-zhengyejian1@huawei.com

Cc: <mhiramat@kernel.org>
Fixes: f1affcaaa861 ("tracing: Add snapshot in the per_cpu trace directories")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
bpf: Clear the probe_addr for uprobe 2023-09-19T10:20:07+00:00 Yafang Shao laoar.shao@gmail.com 2023-07-09T02:56:25+00:00 b275f0ae3598936e37b2cd3b0e862dc40e27be00 [ Upstream commit 5125e757e62f6c1d5478db4c2b61a744060ddf3f ] To avoid returning uninitialized or random values when querying the file descriptor (fd) and accessing probe_addr, it is necessary to clear the variable prior to its use. Fixes: 41bdc4b40ed6 ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY") Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Acked-by: Yonghong Song <yhs@fb.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20230709025630.3735-6-laoar.shao@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 5125e757e62f6c1d5478db4c2b61a744060ddf3f ]

To avoid returning uninitialized or random values when querying the file
descriptor (fd) and accessing probe_addr, it is necessary to clear the
variable prior to its use.

Fixes: 41bdc4b40ed6 ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY")
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230709025630.3735-6-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
tracing: Introduce pipe_cpumask to avoid race on trace_pipes 2023-09-19T10:20:06+00:00 Zheng Yejian zhengyejian1@huawei.com 2023-08-18T02:26:45+00:00 0c0547d2a60aa1d5bd9edb7f14e167d081875eba [ Upstream commit c2489bb7e6be2e8cdced12c16c42fa128403ac03 ] There is race issue when concurrently splice_read main trace_pipe and per_cpu trace_pipes which will result in data read out being different from what actually writen. As suggested by Steven: > I believe we should add a ref count to trace_pipe and the per_cpu > trace_pipes, where if they are opened, nothing else can read it. > > Opening trace_pipe locks all per_cpu ref counts, if any of them are > open, then the trace_pipe open will fail (and releases any ref counts > it had taken). > > Opening a per_cpu trace_pipe will up the ref count for just that > CPU buffer. This will allow multiple tasks to read different per_cpu > trace_pipe files, but will prevent the main trace_pipe file from > being opened. But because we only need to know whether per_cpu trace_pipe is open or not, using a cpumask instead of using ref count may be easier. After this patch, users will find that: - Main trace_pipe can be opened by only one user, and if it is opened, all per_cpu trace_pipes cannot be opened; - Per_cpu trace_pipes can be opened by multiple users, but each per_cpu trace_pipe can only be opened by one user. And if one of them is opened, main trace_pipe cannot be opened. Link: https://lore.kernel.org/linux-trace-kernel/20230818022645.1948314-1-zhengyejian1@huawei.com Suggested-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit c2489bb7e6be2e8cdced12c16c42fa128403ac03 ]

There is race issue when concurrently splice_read main trace_pipe and
per_cpu trace_pipes which will result in data read out being different
from what actually writen.

As suggested by Steven:
  > I believe we should add a ref count to trace_pipe and the per_cpu
  > trace_pipes, where if they are opened, nothing else can read it.
  >
  > Opening trace_pipe locks all per_cpu ref counts, if any of them are
  > open, then the trace_pipe open will fail (and releases any ref counts
  > it had taken).
  >
  > Opening a per_cpu trace_pipe will up the ref count for just that
  > CPU buffer. This will allow multiple tasks to read different per_cpu
  > trace_pipe files, but will prevent the main trace_pipe file from
  > being opened.

But because we only need to know whether per_cpu trace_pipe is open or
not, using a cpumask instead of using ref count may be easier.

After this patch, users will find that:
 - Main trace_pipe can be opened by only one user, and if it is
   opened, all per_cpu trace_pipes cannot be opened;
 - Per_cpu trace_pipes can be opened by multiple users, but each per_cpu
   trace_pipe can only be opened by one user. And if one of them is
   opened, main trace_pipe cannot be opened.

Link: https://lore.kernel.org/linux-trace-kernel/20230818022645.1948314-1-zhengyejian1@huawei.com

Suggested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
tracing: Fix memleak due to race between current_tracer and trace 2023-08-30T14:23:12+00:00 Zheng Yejian zhengyejian1@huawei.com 2023-08-17T12:55:39+00:00 b8205dfed68183dc1470e83863c5ded6d7fa30a9 [ Upstream commit eecb91b9f98d6427d4af5fdb8f108f52572a39e7 ] Kmemleak report a leak in graph_trace_open(): unreferenced object 0xffff0040b95f4a00 (size 128): comm "cat", pid 204981, jiffies 4301155872 (age 99771.964s) hex dump (first 32 bytes): e0 05 e7 b4 ab 7d 00 00 0b 00 01 00 00 00 00 00 .....}.......... f4 00 01 10 00 a0 ff ff 00 00 00 00 65 00 10 00 ............e... backtrace: [<000000005db27c8b>] kmem_cache_alloc_trace+0x348/0x5f0 [<000000007df90faa>] graph_trace_open+0xb0/0x344 [<00000000737524cd>] __tracing_open+0x450/0xb10 [<0000000098043327>] tracing_open+0x1a0/0x2a0 [<00000000291c3876>] do_dentry_open+0x3c0/0xdc0 [<000000004015bcd6>] vfs_open+0x98/0xd0 [<000000002b5f60c9>] do_open+0x520/0x8d0 [<00000000376c7820>] path_openat+0x1c0/0x3e0 [<00000000336a54b5>] do_filp_open+0x14c/0x324 [<000000002802df13>] do_sys_openat2+0x2c4/0x530 [<0000000094eea458>] __arm64_sys_openat+0x130/0x1c4 [<00000000a71d7881>] el0_svc_common.constprop.0+0xfc/0x394 [<00000000313647bf>] do_el0_svc+0xac/0xec [<000000002ef1c651>] el0_svc+0x20/0x30 [<000000002fd4692a>] el0_sync_handler+0xb0/0xb4 [<000000000c309c35>] el0_sync+0x160/0x180 The root cause is descripted as follows: __tracing_open() { // 1. File 'trace' is being opened; ... *iter->trace = *tr->current_trace; // 2. Tracer 'function_graph' is // currently set; ... iter->trace->open(iter); // 3. Call graph_trace_open() here, // and memory are allocated in it; ... } s_start() { // 4. The opened file is being read; ... *iter->trace = *tr->current_trace; // 5. If tracer is switched to // 'nop' or others, then memory // in step 3 are leaked!!! ... } To fix it, in s_start(), close tracer before switching then reopen the new tracer after switching. And some tracers like 'wakeup' may not update 'iter->private' in some cases when reopen, then it should be cleared to avoid being mistakenly closed again. Link: https://lore.kernel.org/linux-trace-kernel/20230817125539.1646321-1-zhengyejian1@huawei.com Fixes: d7350c3f4569 ("tracing/core: make the read callbacks reentrants") Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit eecb91b9f98d6427d4af5fdb8f108f52572a39e7 ]

Kmemleak report a leak in graph_trace_open():

  unreferenced object 0xffff0040b95f4a00 (size 128):
    comm "cat", pid 204981, jiffies 4301155872 (age 99771.964s)
    hex dump (first 32 bytes):
      e0 05 e7 b4 ab 7d 00 00 0b 00 01 00 00 00 00 00 .....}..........
      f4 00 01 10 00 a0 ff ff 00 00 00 00 65 00 10 00 ............e...
    backtrace:
      [<000000005db27c8b>] kmem_cache_alloc_trace+0x348/0x5f0
      [<000000007df90faa>] graph_trace_open+0xb0/0x344
      [<00000000737524cd>] __tracing_open+0x450/0xb10
      [<0000000098043327>] tracing_open+0x1a0/0x2a0
      [<00000000291c3876>] do_dentry_open+0x3c0/0xdc0
      [<000000004015bcd6>] vfs_open+0x98/0xd0
      [<000000002b5f60c9>] do_open+0x520/0x8d0
      [<00000000376c7820>] path_openat+0x1c0/0x3e0
      [<00000000336a54b5>] do_filp_open+0x14c/0x324
      [<000000002802df13>] do_sys_openat2+0x2c4/0x530
      [<0000000094eea458>] __arm64_sys_openat+0x130/0x1c4
      [<00000000a71d7881>] el0_svc_common.constprop.0+0xfc/0x394
      [<00000000313647bf>] do_el0_svc+0xac/0xec
      [<000000002ef1c651>] el0_svc+0x20/0x30
      [<000000002fd4692a>] el0_sync_handler+0xb0/0xb4
      [<000000000c309c35>] el0_sync+0x160/0x180

The root cause is descripted as follows:

  __tracing_open() {  // 1. File 'trace' is being opened;
    ...
    *iter->trace = *tr->current_trace;  // 2. Tracer 'function_graph' is
                                        //    currently set;
    ...
    iter->trace->open(iter);  // 3. Call graph_trace_open() here,
                              //    and memory are allocated in it;
    ...
  }

  s_start() {  // 4. The opened file is being read;
    ...
    *iter->trace = *tr->current_trace;  // 5. If tracer is switched to
                                        //    'nop' or others, then memory
                                        //    in step 3 are leaked!!!
    ...
  }

To fix it, in s_start(), close tracer before switching then reopen the
new tracer after switching. And some tracers like 'wakeup' may not update
'iter->private' in some cases when reopen, then it should be cleared
to avoid being mistakenly closed again.

Link: https://lore.kernel.org/linux-trace-kernel/20230817125539.1646321-1-zhengyejian1@huawei.com

Fixes: d7350c3f4569 ("tracing/core: make the read callbacks reentrants")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
tracing: Fix cpu buffers unavailable due to 'record_disabled' missed 2023-08-30T14:23:12+00:00 Zheng Yejian zhengyejian1@huawei.com 2023-08-05T03:38:15+00:00 9c2ceffd4e36966fa114f3c23f767f2b98fad16f [ Upstream commit b71645d6af10196c46cbe3732de2ea7d36b3ff6d ] Trace ring buffer can no longer record anything after executing following commands at the shell prompt: # cd /sys/kernel/tracing # cat tracing_cpumask fff # echo 0 > tracing_cpumask # echo 1 > snapshot # echo fff > tracing_cpumask # echo 1 > tracing_on # echo "hello world" > trace_marker -bash: echo: write error: Bad file descriptor The root cause is that: 1. After `echo 0 > tracing_cpumask`, 'record_disabled' of cpu buffers in 'tr->array_buffer.buffer' became 1 (see tracing_set_cpumask()); 2. After `echo 1 > snapshot`, 'tr->array_buffer.buffer' is swapped with 'tr->max_buffer.buffer', then the 'record_disabled' became 0 (see update_max_tr()); 3. After `echo fff > tracing_cpumask`, the 'record_disabled' become -1; Then array_buffer and max_buffer are both unavailable due to value of 'record_disabled' is not 0. To fix it, enable or disable both array_buffer and max_buffer at the same time in tracing_set_cpumask(). Link: https://lkml.kernel.org/r/20230805033816.3284594-2-zhengyejian1@huawei.com Cc: <mhiramat@kernel.org> Cc: <vnagarnaik@google.com> Cc: <shuah@kernel.org> Fixes: 71babb2705e2 ("tracing: change CPU ring buffer state from tracing_cpumask") Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit b71645d6af10196c46cbe3732de2ea7d36b3ff6d ]

Trace ring buffer can no longer record anything after executing
following commands at the shell prompt:

  # cd /sys/kernel/tracing
  # cat tracing_cpumask
  fff
  # echo 0 > tracing_cpumask
  # echo 1 > snapshot
  # echo fff > tracing_cpumask
  # echo 1 > tracing_on
  # echo "hello world" > trace_marker
  -bash: echo: write error: Bad file descriptor

The root cause is that:
  1. After `echo 0 > tracing_cpumask`, 'record_disabled' of cpu buffers
     in 'tr->array_buffer.buffer' became 1 (see tracing_set_cpumask());
  2. After `echo 1 > snapshot`, 'tr->array_buffer.buffer' is swapped
     with 'tr->max_buffer.buffer', then the 'record_disabled' became 0
     (see update_max_tr());
  3. After `echo fff > tracing_cpumask`, the 'record_disabled' become -1;
Then array_buffer and max_buffer are both unavailable due to value of
'record_disabled' is not 0.

To fix it, enable or disable both array_buffer and max_buffer at the same
time in tracing_set_cpumask().

Link: https://lkml.kernel.org/r/20230805033816.3284594-2-zhengyejian1@huawei.com

Cc: <mhiramat@kernel.org>
Cc: <vnagarnaik@google.com>
Cc: <shuah@kernel.org>
Fixes: 71babb2705e2 ("tracing: change CPU ring buffer state from tracing_cpumask")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
tracing/probes: Fix to update dynamic data counter if fetcharg uses it 2023-08-26T13:26:50+00:00 Masami Hiramatsu (Google) mhiramat@kernel.org 2023-07-11T14:15:48+00:00 3b76d92636791261c004979fd1c94edc68058d3e [ Upstream commit e38e2c6a9efc435f9de344b7c91f7697e01b47d5 ] Fix to update dynamic data counter ('dyndata') and max length ('maxlen') only if the fetcharg uses the dynamic data. Also get out arg->dynamic from unlikely(). This makes dynamic data address wrong if process_fetch_insn() returns error on !arg->dynamic case. Link: https://lore.kernel.org/all/168908494781.123124.8160245359962103684.stgit@devnote2/ Suggested-by: Steven Rostedt <rostedt@goodmis.org> Link: https://lore.kernel.org/all/20230710233400.5aaf024e@gandalf.local.home/ Fixes: 9178412ddf5a ("tracing: probeevent: Return consumed bytes of dynamic area") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit e38e2c6a9efc435f9de344b7c91f7697e01b47d5 ]

Fix to update dynamic data counter ('dyndata') and max length ('maxlen')
only if the fetcharg uses the dynamic data. Also get out arg->dynamic
from unlikely(). This makes dynamic data address wrong if
process_fetch_insn() returns error on !arg->dynamic case.

Link: https://lore.kernel.org/all/168908494781.123124.8160245359962103684.stgit@devnote2/

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Link: https://lore.kernel.org/all/20230710233400.5aaf024e@gandalf.local.home/
Fixes: 9178412ddf5a ("tracing: probeevent: Return consumed bytes of dynamic area")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
tracing/probes: Have process_fetch_insn() take a void * instead of pt_regs 2023-08-26T13:26:50+00:00 Steven Rostedt (VMware) rostedt@goodmis.org 2021-08-19T04:13:28+00:00 265a979dedb123aba2480112cf0288ebf348de84 [ Upstream commit 8565a45d0858078b63c7d84074a21a42ba9ebf01 ] In preparation to allow event probes to use the process_fetch_insn() callback in trace_probe_tmpl.h, change the data passed to it from a pointer to pt_regs, as the event probe will not be using regs, and make it a void pointer instead. Update the process_fetch_insn() callers for kprobe and uprobe events to have the regs defined in the function and just typecast the void pointer parameter. Link: https://lkml.kernel.org/r/20210819041842.291622924@goodmis.org Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Stable-dep-of: e38e2c6a9efc ("tracing/probes: Fix to update dynamic data counter if fetcharg uses it") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 8565a45d0858078b63c7d84074a21a42ba9ebf01 ]

In preparation to allow event probes to use the process_fetch_insn()
callback in trace_probe_tmpl.h, change the data passed to it from a
pointer to pt_regs, as the event probe will not be using regs, and make it
a void pointer instead.

Update the process_fetch_insn() callers for kprobe and uprobe events to
have the regs defined in the function and just typecast the void pointer
parameter.

Link: https://lkml.kernel.org/r/20210819041842.291622924@goodmis.org

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Stable-dep-of: e38e2c6a9efc ("tracing/probes: Fix to update dynamic data counter if fetcharg uses it")
Signed-off-by: Sasha Levin <sashal@kernel.org>
ring-buffer: Do not swap cpu_buffer during resize process 2023-08-26T13:26:46+00:00 Chen Lin chen.lin5@zte.com.cn 2023-07-19T07:58:47+00:00 66a3b2a121386702663065d5c9e5a33c03d3f4a2 [ Upstream commit 8a96c0288d0737ad77882024974c075345c72011 ] When ring_buffer_swap_cpu was called during resize process, the cpu buffer was swapped in the middle, resulting in incorrect state. Continuing to run in the wrong state will result in oops. This issue can be easily reproduced using the following two scripts: /tmp # cat test1.sh //#! /bin/sh for i in `seq 0 100000` do echo 2000 > /sys/kernel/debug/tracing/buffer_size_kb sleep 0.5 echo 5000 > /sys/kernel/debug/tracing/buffer_size_kb sleep 0.5 done /tmp # cat test2.sh //#! /bin/sh for i in `seq 0 100000` do echo irqsoff > /sys/kernel/debug/tracing/current_tracer sleep 1 echo nop > /sys/kernel/debug/tracing/current_tracer sleep 1 done /tmp # ./test1.sh & /tmp # ./test2.sh & A typical oops log is as follows, sometimes with other different oops logs. [ 231.711293] WARNING: CPU: 0 PID: 9 at kernel/trace/ring_buffer.c:2026 rb_update_pages+0x378/0x3f8 [ 231.713375] Modules linked in: [ 231.714735] CPU: 0 PID: 9 Comm: kworker/0:1 Tainted: G W 6.5.0-rc1-00276-g20edcec23f92 #15 [ 231.716750] Hardware name: linux,dummy-virt (DT) [ 231.718152] Workqueue: events update_pages_handler [ 231.719714] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 231.721171] pc : rb_update_pages+0x378/0x3f8 [ 231.722212] lr : rb_update_pages+0x25c/0x3f8 [ 231.723248] sp : ffff800082b9bd50 [ 231.724169] x29: ffff800082b9bd50 x28: ffff8000825f7000 x27: 0000000000000000 [ 231.726102] x26: 0000000000000001 x25: fffffffffffff010 x24: 0000000000000ff0 [ 231.728122] x23: ffff0000c3a0b600 x22: ffff0000c3a0b5c0 x21: fffffffffffffe0a [ 231.730203] x20: ffff0000c3a0b600 x19: ffff0000c0102400 x18: 0000000000000000 [ 231.732329] x17: 0000000000000000 x16: 0000000000000000 x15: 0000ffffe7aa8510 [ 231.734212] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000002 [ 231.736291] x11: ffff8000826998a8 x10: ffff800082b9baf0 x9 : ffff800081137558 [ 231.738195] x8 : fffffc00030e82c8 x7 : 0000000000000000 x6 : 0000000000000001 [ 231.740192] x5 : ffff0000ffbafe00 x4 : 0000000000000000 x3 : 0000000000000000 [ 231.742118] x2 : 00000000000006aa x1 : 0000000000000001 x0 : ffff0000c0007208 [ 231.744196] Call trace: [ 231.744892] rb_update_pages+0x378/0x3f8 [ 231.745893] update_pages_handler+0x1c/0x38 [ 231.746893] process_one_work+0x1f0/0x468 [ 231.747852] worker_thread+0x54/0x410 [ 231.748737] kthread+0x124/0x138 [ 231.749549] ret_from_fork+0x10/0x20 [ 231.750434] ---[ end trace 0000000000000000 ]--- [ 233.720486] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 233.721696] Mem abort info: [ 233.721935] ESR = 0x0000000096000004 [ 233.722283] EC = 0x25: DABT (current EL), IL = 32 bits [ 233.722596] SET = 0, FnV = 0 [ 233.722805] EA = 0, S1PTW = 0 [ 233.723026] FSC = 0x04: level 0 translation fault [ 233.723458] Data abort info: [ 233.723734] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 [ 233.724176] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 233.724589] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 233.725075] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000104943000 [ 233.725592] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000 [ 233.726231] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP [ 233.726720] Modules linked in: [ 233.727007] CPU: 0 PID: 9 Comm: kworker/0:1 Tainted: G W 6.5.0-rc1-00276-g20edcec23f92 #15 [ 233.727777] Hardware name: linux,dummy-virt (DT) [ 233.728225] Workqueue: events update_pages_handler [ 233.728655] pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 233.729054] pc : rb_update_pages+0x1a8/0x3f8 [ 233.729334] lr : rb_update_pages+0x154/0x3f8 [ 233.729592] sp : ffff800082b9bd50 [ 233.729792] x29: ffff800082b9bd50 x28: ffff8000825f7000 x27: 0000000000000000 [ 233.730220] x26: 0000000000000000 x25: ffff800082a8b840 x24: ffff0000c0102418 [ 233.730653] x23: 0000000000000000 x22: fffffc000304c880 x21: 0000000000000003 [ 233.731105] x20: 00000000000001f4 x19: ffff0000c0102400 x18: ffff800082fcbc58 [ 233.731727] x17: 0000000000000000 x16: 0000000000000001 x15: 0000000000000001 [ 233.732282] x14: ffff8000825fe0c8 x13: 0000000000000001 x12: 0000000000000000 [ 233.732709] x11: ffff8000826998a8 x10: 0000000000000ae0 x9 : ffff8000801b760c [ 233.733148] x8 : fefefefefefefeff x7 : 0000000000000018 x6 : ffff0000c03298c0 [ 233.733553] x5 : 0000000000000002 x4 : 0000000000000000 x3 : 0000000000000000 [ 233.733972] x2 : ffff0000c3a0b600 x1 : 0000000000000000 x0 : 0000000000000000 [ 233.734418] Call trace: [ 233.734593] rb_update_pages+0x1a8/0x3f8 [ 233.734853] update_pages_handler+0x1c/0x38 [ 233.735148] process_one_work+0x1f0/0x468 [ 233.735525] worker_thread+0x54/0x410 [ 233.735852] kthread+0x124/0x138 [ 233.736064] ret_from_fork+0x10/0x20 [ 233.736387] Code: 92400000 910006b5 aa000021 aa0303f7 (f9400060) [ 233.736959] ---[ end trace 0000000000000000 ]--- After analysis, the seq of the error is as follows [1-5]: int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size, int cpu_id) { for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; //1. get cpu_buffer, aka cpu_buffer(A) ... ... schedule_work_on(cpu, &cpu_buffer->update_pages_work); //2. 'update_pages_work' is queue on 'cpu', cpu_buffer(A) is passed to // update_pages_handler, do the update process, set 'update_done' in // complete(&cpu_buffer->update_done) and to wakeup resize process. //----> //3. Just at this moment, ring_buffer_swap_cpu is triggered, //cpu_buffer(A) be swaped to cpu_buffer(B), the max_buffer. //ring_buffer_swap_cpu is called as the 'Call trace' below. Call trace: dump_backtrace+0x0/0x2f8 show_stack+0x18/0x28 dump_stack+0x12c/0x188 ring_buffer_swap_cpu+0x2f8/0x328 update_max_tr_single+0x180/0x210 check_critical_timing+0x2b4/0x2c8 tracer_hardirqs_on+0x1c0/0x200 trace_hardirqs_on+0xec/0x378 el0_svc_common+0x64/0x260 do_el0_svc+0x90/0xf8 el0_svc+0x20/0x30 el0_sync_handler+0xb0/0xb8 el0_sync+0x180/0x1c0 //<---- /* wait for all the updates to complete */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; //4. get cpu_buffer, cpu_buffer(B) is used in the following process, //the state of cpu_buffer(A) and cpu_buffer(B) is totally wrong. //for example, cpu_buffer(A)->update_done will leave be set 1, and will //not 'wait_for_completion' at the next resize round. if (!cpu_buffer->nr_pages_to_update) continue; if (cpu_online(cpu)) wait_for_completion(&cpu_buffer->update_done); cpu_buffer->nr_pages_to_update = 0; } ... } //5. the state of cpu_buffer(A) and cpu_buffer(B) is totally wrong, //Continuing to run in the wrong state, then oops occurs. Link: https://lore.kernel.org/linux-trace-kernel/202307191558478409990@zte.com.cn Signed-off-by: Chen Lin <chen.lin5@zte.com.cn> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 8a96c0288d0737ad77882024974c075345c72011 ]

When ring_buffer_swap_cpu was called during resize process,
the cpu buffer was swapped in the middle, resulting in incorrect state.
Continuing to run in the wrong state will result in oops.

This issue can be easily reproduced using the following two scripts:
/tmp # cat test1.sh
//#! /bin/sh
for i in `seq 0 100000`
do
         echo 2000 > /sys/kernel/debug/tracing/buffer_size_kb
         sleep 0.5
         echo 5000 > /sys/kernel/debug/tracing/buffer_size_kb
         sleep 0.5
done
/tmp # cat test2.sh
//#! /bin/sh
for i in `seq 0 100000`
do
        echo irqsoff > /sys/kernel/debug/tracing/current_tracer
        sleep 1
        echo nop > /sys/kernel/debug/tracing/current_tracer
        sleep 1
done
/tmp # ./test1.sh &
/tmp # ./test2.sh &

A typical oops log is as follows, sometimes with other different oops logs.

[  231.711293] WARNING: CPU: 0 PID: 9 at kernel/trace/ring_buffer.c:2026 rb_update_pages+0x378/0x3f8
[  231.713375] Modules linked in:
[  231.714735] CPU: 0 PID: 9 Comm: kworker/0:1 Tainted: G        W          6.5.0-rc1-00276-g20edcec23f92 #15
[  231.716750] Hardware name: linux,dummy-virt (DT)
[  231.718152] Workqueue: events update_pages_handler
[  231.719714] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  231.721171] pc : rb_update_pages+0x378/0x3f8
[  231.722212] lr : rb_update_pages+0x25c/0x3f8
[  231.723248] sp : ffff800082b9bd50
[  231.724169] x29: ffff800082b9bd50 x28: ffff8000825f7000 x27: 0000000000000000
[  231.726102] x26: 0000000000000001 x25: fffffffffffff010 x24: 0000000000000ff0
[  231.728122] x23: ffff0000c3a0b600 x22: ffff0000c3a0b5c0 x21: fffffffffffffe0a
[  231.730203] x20: ffff0000c3a0b600 x19: ffff0000c0102400 x18: 0000000000000000
[  231.732329] x17: 0000000000000000 x16: 0000000000000000 x15: 0000ffffe7aa8510
[  231.734212] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000002
[  231.736291] x11: ffff8000826998a8 x10: ffff800082b9baf0 x9 : ffff800081137558
[  231.738195] x8 : fffffc00030e82c8 x7 : 0000000000000000 x6 : 0000000000000001
[  231.740192] x5 : ffff0000ffbafe00 x4 : 0000000000000000 x3 : 0000000000000000
[  231.742118] x2 : 00000000000006aa x1 : 0000000000000001 x0 : ffff0000c0007208
[  231.744196] Call trace:
[  231.744892]  rb_update_pages+0x378/0x3f8
[  231.745893]  update_pages_handler+0x1c/0x38
[  231.746893]  process_one_work+0x1f0/0x468
[  231.747852]  worker_thread+0x54/0x410
[  231.748737]  kthread+0x124/0x138
[  231.749549]  ret_from_fork+0x10/0x20
[  231.750434] ---[ end trace 0000000000000000 ]---
[  233.720486] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[  233.721696] Mem abort info:
[  233.721935]   ESR = 0x0000000096000004
[  233.722283]   EC = 0x25: DABT (current EL), IL = 32 bits
[  233.722596]   SET = 0, FnV = 0
[  233.722805]   EA = 0, S1PTW = 0
[  233.723026]   FSC = 0x04: level 0 translation fault
[  233.723458] Data abort info:
[  233.723734]   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[  233.724176]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[  233.724589]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[  233.725075] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000104943000
[  233.725592] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
[  233.726231] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[  233.726720] Modules linked in:
[  233.727007] CPU: 0 PID: 9 Comm: kworker/0:1 Tainted: G        W          6.5.0-rc1-00276-g20edcec23f92 #15
[  233.727777] Hardware name: linux,dummy-virt (DT)
[  233.728225] Workqueue: events update_pages_handler
[  233.728655] pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[  233.729054] pc : rb_update_pages+0x1a8/0x3f8
[  233.729334] lr : rb_update_pages+0x154/0x3f8
[  233.729592] sp : ffff800082b9bd50
[  233.729792] x29: ffff800082b9bd50 x28: ffff8000825f7000 x27: 0000000000000000
[  233.730220] x26: 0000000000000000 x25: ffff800082a8b840 x24: ffff0000c0102418
[  233.730653] x23: 0000000000000000 x22: fffffc000304c880 x21: 0000000000000003
[  233.731105] x20: 00000000000001f4 x19: ffff0000c0102400 x18: ffff800082fcbc58
[  233.731727] x17: 0000000000000000 x16: 0000000000000001 x15: 0000000000000001
[  233.732282] x14: ffff8000825fe0c8 x13: 0000000000000001 x12: 0000000000000000
[  233.732709] x11: ffff8000826998a8 x10: 0000000000000ae0 x9 : ffff8000801b760c
[  233.733148] x8 : fefefefefefefeff x7 : 0000000000000018 x6 : ffff0000c03298c0
[  233.733553] x5 : 0000000000000002 x4 : 0000000000000000 x3 : 0000000000000000
[  233.733972] x2 : ffff0000c3a0b600 x1 : 0000000000000000 x0 : 0000000000000000
[  233.734418] Call trace:
[  233.734593]  rb_update_pages+0x1a8/0x3f8
[  233.734853]  update_pages_handler+0x1c/0x38
[  233.735148]  process_one_work+0x1f0/0x468
[  233.735525]  worker_thread+0x54/0x410
[  233.735852]  kthread+0x124/0x138
[  233.736064]  ret_from_fork+0x10/0x20
[  233.736387] Code: 92400000 910006b5 aa000021 aa0303f7 (f9400060)
[  233.736959] ---[ end trace 0000000000000000 ]---

After analysis, the seq of the error is as follows [1-5]:

int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
			int cpu_id)
{
	for_each_buffer_cpu(buffer, cpu) {
		cpu_buffer = buffer->buffers[cpu];
		//1. get cpu_buffer, aka cpu_buffer(A)
		...
		...
		schedule_work_on(cpu,
		 &cpu_buffer->update_pages_work);
		//2. 'update_pages_work' is queue on 'cpu', cpu_buffer(A) is passed to
		// update_pages_handler, do the update process, set 'update_done' in
		// complete(&cpu_buffer->update_done) and to wakeup resize process.
	//---->
		//3. Just at this moment, ring_buffer_swap_cpu is triggered,
		//cpu_buffer(A) be swaped to cpu_buffer(B), the max_buffer.
		//ring_buffer_swap_cpu is called as the 'Call trace' below.

		Call trace:
		 dump_backtrace+0x0/0x2f8
		 show_stack+0x18/0x28
		 dump_stack+0x12c/0x188
		 ring_buffer_swap_cpu+0x2f8/0x328
		 update_max_tr_single+0x180/0x210
		 check_critical_timing+0x2b4/0x2c8
		 tracer_hardirqs_on+0x1c0/0x200
		 trace_hardirqs_on+0xec/0x378
		 el0_svc_common+0x64/0x260
		 do_el0_svc+0x90/0xf8
		 el0_svc+0x20/0x30
		 el0_sync_handler+0xb0/0xb8
		 el0_sync+0x180/0x1c0
	//<----

	/* wait for all the updates to complete */
	for_each_buffer_cpu(buffer, cpu) {
		cpu_buffer = buffer->buffers[cpu];
		//4. get cpu_buffer, cpu_buffer(B) is used in the following process,
		//the state of cpu_buffer(A) and cpu_buffer(B) is totally wrong.
		//for example, cpu_buffer(A)->update_done will leave be set 1, and will
		//not 'wait_for_completion' at the next resize round.
		  if (!cpu_buffer->nr_pages_to_update)
			continue;

		if (cpu_online(cpu))
			wait_for_completion(&cpu_buffer->update_done);
		cpu_buffer->nr_pages_to_update = 0;
	}
	...
}
	//5. the state of cpu_buffer(A) and cpu_buffer(B) is totally wrong,
	//Continuing to run in the wrong state, then oops occurs.

Link: https://lore.kernel.org/linux-trace-kernel/202307191558478409990@zte.com.cn

Signed-off-by: Chen Lin <chen.lin5@zte.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
tracing: Fix sleeping while atomic in kdb ftdump 2023-08-11T09:57:53+00:00 Douglas Anderson dianders@chromium.org 2022-07-09T00:09:52+00:00 426656e8dd03ded47112e5e1488f0975a1f0d806 commit 495fcec8648cdfb483b5b9ab310f3839f07cb3b8 upstream. If you drop into kdb and type "ftdump" you'll get a sleeping while atomic warning from memory allocation in trace_find_next_entry(). This appears to have been caused by commit ff895103a84a ("tracing: Save off entry when peeking at next entry"), which added the allocation in that path. The problematic commit was already fixed by commit 8e99cf91b99b ("tracing: Do not allocate buffer in trace_find_next_entry() in atomic") but that fix missed the kdb case. The fix here is easy: just move the assignment of the static buffer to the place where it should have been to begin with: trace_init_global_iter(). That function is called in two places, once is right before the assignment of the static buffer added by the previous fix and once is in kdb. Note that it appears that there's a second static buffer that we need to assign that was added in commit efbbdaa22bb7 ("tracing: Show real address for trace event arguments"), so we'll move that too. Link: https://lkml.kernel.org/r/20220708170919.1.I75844e5038d9425add2ad853a608cb44bb39df40@changeid Fixes: ff895103a84a ("tracing: Save off entry when peeking at next entry") Fixes: efbbdaa22bb7 ("tracing: Show real address for trace event arguments") Signed-off-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 495fcec8648cdfb483b5b9ab310f3839f07cb3b8 upstream.

If you drop into kdb and type "ftdump" you'll get a sleeping while
atomic warning from memory allocation in trace_find_next_entry().

This appears to have been caused by commit ff895103a84a ("tracing:
Save off entry when peeking at next entry"), which added the
allocation in that path. The problematic commit was already fixed by
commit 8e99cf91b99b ("tracing: Do not allocate buffer in
trace_find_next_entry() in atomic") but that fix missed the kdb case.

The fix here is easy: just move the assignment of the static buffer to
the place where it should have been to begin with:
trace_init_global_iter(). That function is called in two places, once
is right before the assignment of the static buffer added by the
previous fix and once is in kdb.

Note that it appears that there's a second static buffer that we need
to assign that was added in commit efbbdaa22bb7 ("tracing: Show real
address for trace event arguments"), so we'll move that too.

Link: https://lkml.kernel.org/r/20220708170919.1.I75844e5038d9425add2ad853a608cb44bb39df40@changeid

Fixes: ff895103a84a ("tracing: Save off entry when peeking at next entry")
Fixes: efbbdaa22bb7 ("tracing: Show real address for trace event arguments")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>