[LU-20168] debugfs entries for fldb should be pinned

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

Description

otherwise racing umount can free internal structures these entries access:

[  760.524901] general protection fault, probably for non-canonical address 0x5a5a5a5a5a5a5a5a: 0000 [#1] PREEMPT SMP
[  760.525318] CPU: 0 PID: 208503 Comm: lctl Tainted: G        W  O      -------- -  - 4.18.0 #1
[  760.525825] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014
[  760.525856] RIP: 0010:fldb_seq_release+0x32/0x1c0 [fid]
[  760.525914] Code: f5 53 48 8b 86 a8 01 00 00 48 8b 98 e8 00 00 00 48 85 db 0f 84 98 00 00 00 48 8b 43 40 48 8b 40 08 48 85 c0 0f 84 fe 00 00 00 <48> 8b 40 38 48 83 f8 d8 0f 84 20 01 00 00 48 8b 73 38 48 85 f6 0f
[  760.526097] RSP: 0018:ffff90486b87be50 EFLAGS: 00010206
[  760.526112] RAX: 5a5a5a5a5a5a5a5a RBX: ffff90486a0c8e80 RCX: 0000000000000001
[  760.526134] RDX: ffff904846bf79b0 RSI: ffff904846bf7800 RDI: ffff90485793aa60
[  760.526156] RBP: ffff904846bf7800 R08: 0000000000000000 R09: 0000000000000000
[  760.526178] R10: 0000000000000000 R11: 0000000000000000 R12: ffff90485793aa60
[  760.526203] R13: ffff90484f7cc600 R14: ffff904846f928e0 R15: ffff90484da78d10
[  760.526231] FS:  00007f3808785740(0000) GS:ffff904950800000(0000) knlGS:0000000000000000
[  760.526254] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  760.526274] CR2: 000055c8cdbaa838 CR3: 000000011780a000 CR4: 0000000000350eb0
[  760.526297] Call Trace:
[  760.526319]  ? __die_body+0x15/0x60
[  760.526341]  ? die_addr+0x33/0x4c
[  760.526365]  ? do_general_protection+0x15f/0x300
[  760.526442]  ? general_protection+0x1e/0x30
[  760.526459]  ? fldb_seq_release+0x32/0x1c0 [fid]
[  760.526487]  full_proxy_release+0x33/0xa0
[  760.526566]  __fput+0xc5/0x260
[  760.526682]  task_work_run+0x8a/0xc0
[  760.526817]  exit_to_usermode_loop+0xc5/0xd0
[  760.526952]  do_syscall_64+0x157/0x1d0
[  760.526966]  entry_SYSCALL_64_after_h

Issue Links

• duplicates: LU-20162 debugfs files should pin themselves