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tracing/timerlat: Move hrtimer_init to timerlat_fd open()

John Kacur requested to merge jkacur/centos-stream-9:RHEL-28655 into main

JIRA: https://issues.redhat.com/browse/RHEL-28655

commit 1389358bb008e7625942846e9f03554319b7fecc
Author: Daniel Bristot de Oliveira bristot@kernel.org
Date: Thu Feb 1 16:13:39 2024 +0100

tracing/timerlat: Move hrtimer_init to timerlat_fd open()

tracing/timerlat: Move hrtimer_init to timerlat_fd open()  

Currently, the timerlat's hrtimer is initialized at the first read of  
timerlat_fd, and destroyed at close(). It works, but it causes an error  
if the user program open() and close() the file without reading.  

Here's an example:  

 timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r')  
 timerlat_fd.close();  
 EOF  
<BOOM>  

 BUG: kernel NULL pointer dereference, address: 0000000000000010  
 PGD 0 P4D 0  
 Oops: 0000 [#1] PREEMPT SMP NOPTI  
 CPU: 1 PID: 2673 Comm: python3 Not tainted 6.6.13-200.fc39.x86_64 #1  
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-1.fc39 04/01/2014  
 RIP: 0010:hrtimer_active+0xd/0x50  
 Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 57 30 <8b> 42 10 a8 01 74 09 f3 90 8b 42 10 a8 01 75 f7 80 7f 38 00 75 1d  
 RSP: 0018:ffffb031009b7e10 EFLAGS: 00010286  
 RAX: 000000000002db00 RBX: ffff9118f786db08 RCX: 0000000000000000  
 RDX: 0000000000000000 RSI: ffff9117a0e64400 RDI: ffff9118f786db08  
 RBP: ffff9118f786db80 R08: ffff9117a0ddd420 R09: ffff9117804d4f70  
 R10: 0000000000000000 R11: 0000000000000000 R12: ffff9118f786db08  
 R13: ffff91178fdd5e20 R14: ffff9117840978c0 R15: 0000000000000000  
 FS:  00007f2ffbab1740(0000) GS:ffff9118f7840000(0000) knlGS:0000000000000000  
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033  
 CR2: 0000000000000010 CR3: 00000001b402e000 CR4: 0000000000750ee0  
 PKRU: 55555554  
 Call Trace:  
  <TASK>  
  ? __die+0x23/0x70  
  ? page_fault_oops+0x171/0x4e0  
  ? srso_alias_return_thunk+0x5/0x7f  
  ? avc_has_extended_perms+0x237/0x520  
  ? exc_page_fault+0x7f/0x180  
  ? asm_exc_page_fault+0x26/0x30  
  ? hrtimer_active+0xd/0x50  
  hrtimer_cancel+0x15/0x40  
  timerlat_fd_release+0x48/0xe0  
  __fput+0xf5/0x290  
  __x64_sys_close+0x3d/0x80  
  do_syscall_64+0x60/0x90  
  ? srso_alias_return_thunk+0x5/0x7f  
  ? __x64_sys_ioctl+0x72/0xd0  
  ? srso_alias_return_thunk+0x5/0x7f  
  ? syscall_exit_to_user_mode+0x2b/0x40  
  ? srso_alias_return_thunk+0x5/0x7f  
  ? do_syscall_64+0x6c/0x90  
  ? srso_alias_return_thunk+0x5/0x7f  
  ? exit_to_user_mode_prepare+0x142/0x1f0  
  ? srso_alias_return_thunk+0x5/0x7f  
  ? syscall_exit_to_user_mode+0x2b/0x40  
  ? srso_alias_return_thunk+0x5/0x7f  
  ? do_syscall_64+0x6c/0x90  
  entry_SYSCALL_64_after_hwframe+0x6e/0xd8  
 RIP: 0033:0x7f2ffb321594  
 Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 cd 0d 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 3c c3 0f 1f 00 55 48 89 e5 48 83 ec 10 89 7d  
 RSP: 002b:00007ffe8d8eef18 EFLAGS: 00000202 ORIG_RAX: 0000000000000003  
 RAX: ffffffffffffffda RBX: 00007f2ffba4e668 RCX: 00007f2ffb321594  
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003  
 RBP: 00007ffe8d8eef40 R08: 0000000000000000 R09: 0000000000000000  
 R10: 55c926e3167eae79 R11: 0000000000000202 R12: 0000000000000003  
 R13: 00007ffe8d8ef030 R14: 0000000000000000 R15: 00007f2ffba4e668  
  </TASK>  
 CR2: 0000000000000010  
 ---[ end trace 0000000000000000 ]---  

Move hrtimer_init to timerlat_fd open() to avoid this problem.  

Link: https://lore.kernel.org/linux-trace-kernel/7324dd3fc0035658c99b825204a66049389c56e3.1706798888.git.bristot@kernel.org  

Cc: Masami Hiramatsu <mhiramat@kernel.org>  
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>  
Cc: stable@vger.kernel.org  
Fixes: e88ed227f639 ("tracing/timerlat: Add user-space interface")  
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>  
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Signed-off-by: John Kacur jkacur@redhat.com

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