[LU-20162] debugfs files should pin themselves

• Type: Bug
• Resolution: Unresolved
• Priority: Medium
• Severity: 3
• Assignee: WC Triage
• Reporter: Alex Zhuravlev

Description

debugfs files should pin themselves to prevent memory release from a racing umount like this:

[  348.500446] general protection fault, probably for non-canonical address 0x5a5a5a5a5a5a5a5a: 0000 [#1] PREEMPT SMP
[  348.500594] CPU: 0 PID: 75267 Comm: lctl Tainted: G        W  O      -------- -  - 4.18.0 #1
[  348.500657] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014
[  348.500713] RIP: 0010:fldb_seq_release+0x32/0x1c0 [fld]
[  348.518018] Code: f5 53 48 8b 86 a8 01 00 00 48 8b 98 e8 00 00 00 48 85 db 0f 84 94 00 00 00 48 8b 43 40 48 8b 40 08 48 85 c0 0f 84 fb 00 00 00 <48> 8b 40 38 48 83 f8 d8 0f 84 1d 01 00 00 48 8b 73 38 48 85 f6 0f
[  348.518123] RSP: 0018:ffff989e88b5fe50 EFLAGS: 00010206
[  348.518160] RAX: 5a5a5a5a5a5a5a5a RBX: ffff989e6edafc80 RCX: 0000000000000001
[  348.518210] RDX: ffff989e92e4f7b0 RSI: ffff989e92e4f600 RDI: ffff989e75bdd920
[  348.518257] RBP: ffff989e92e4f600 R08: 0000000000000000 R09: 0000000000000000
[  348.518305] R10: 0000000000000000 R11: 0000000000000000 R12: ffff989e75bdd920
[  348.518352] R13: ffff989e6fb6fc00 R14: ffff989f05f98aa0 R15: ffff989e75ae92a0
[  348.518400] FS:  00007fc427eb6740(0000) GS:ffff989f90800000(0000) knlGS:0000000000000000
[  348.518448] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  348.518489] CR2: 00000000006930a8 CR3: 000000013011e000 CR4: 0000000000350eb0
[  348.518537] Call Trace:
[  348.518567]  ? __die_body+0x15/0x60
[  348.518602]  ? die_addr+0x33/0x4c
[  348.518632]  ? do_general_protection+0x15f/0x300
[  348.518671]  ? general_protection+0x1e/0x30
[  348.518705]  ? fldb_seq_release+0x32/0x1c0 [fld]
[  348.518746]  full_proxy_release+0x33/0xa0
[  348.518800]  __fput+0xc5/0x260
[  348.518834]  task_work_run+0x8a/0xc0
[  348.518874]  exit_to_usermode_loop+0xc5/0xd0
[  348.518922]  do_syscall_64+0x157/0x1d0
[  348.518952]  entry_SYSCALL_64_after_hwframe+0x4e/0xc3

Issue Links

• is duplicated by: LU-20168 debugfs entries for fldb should be pinned