[LU-20063] BUG: kernel NULL pointer dereference in max_easize_show()

• Type: Bug
• Resolution: Fixed
• Priority: Medium
• Fix Version/s: Lustre 2.18.0
• Severity: 3
• Assignee: Alex Zhuravlev
• Reporter: Alex Zhuravlev

Description

[   66.966799] BUG: kernel NULL pointer dereference, address: 0000000000000110
[   66.966803] #PF: supervisor read access in kernel mode
[   66.966804] #PF: error_code(0x0000) - not-present page
[   66.966805] PGD 159d23067 P4D 159d23067 PUD 159d22067 PMD 0 
[   66.966808] Oops: 0000 [#1] SMP
[   66.966811] CPU: 1 PID: 8893 Comm: lctl Tainted: G        W  O      -------  ---  5.14.0 #24
[   66.966813] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014
[   66.966814] RIP: 0010:ll_get_max_mdsize+0x23d/0x2a0 [lustre]
[   66.966845] Code: 00 00 00 48 c7 c7 a0 9e 0a c1 48 c7 05 60 06 08 00 10 5d 0e c1 c7 05 66 06 08 00 00 00 02 00 48 c7 05 63 06 08 00 90 9e 0a c1 <48> 8b 90 10 01 00 00 48 83 c2 40 e8 e3 c8 01 ff f6 05 dc 1c 02 ff
[   66.966846] RSP: 0018:ffff8fedf4bbbdc8 EFLAGS: 00010286
[   66.966848] RAX: 0000000000000000 RBX: ffff8fedf4bbbdf4 RCX: 00000000ffffffed
[   66.966849] RDX: 0000000000000000 RSI: ffffffffc10ed8d0 RDI: ffffffffc10a9ea0
[   66.966850] RBP: ffff8fedc78db000 R08: ffff8fedc4fb8000 R09: 0000000000000000
[   66.966851] R10: ffffffffffffffff R11: ffff8fedc4fb73d1 R12: 00000000ffffffed
[   66.966851] R13: ffff8fedc78db3a8 R14: ffff8fee1ae8ec00 R15: 0000000000000001
[   66.966854] FS:  00007fcdd46f5940(0000) GS:ffff8fef10900000(0000) knlGS:0000000000000000
[   66.966856] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   66.966857] CR2: 0000000000000110 CR3: 000000010cd1c000 CR4: 0000000000350eb0
[   66.966860] Call Trace:
[   66.966862]  <TASK>
[   66.966864]  ? __die_body.cold+0x1a/0x1f
[   66.966868]  ? page_fault_oops+0x65/0x1d0
[   66.966872]  ? exc_page_fault+0x65/0x240
[   66.966876]  ? asm_exc_page_fault+0x22/0x30
[   66.966879]  ? ll_get_max_mdsize+0x23d/0x2a0 [lustre]
[   66.966903]  ? ll_get_max_mdsize+0x36/0x2a0 [lustre]
[   66.966928]  max_easize_show+0x19/0x50 [lustre]
[   66.966955]  ? kernfs_get_active+0x51/0x70
[   66.966958]  sysfs_kf_seq_show+0x92/0xd0
[   66.966960]  seq_read_iter+0x100/0x460
[   66.966964]  vfs_read+0x229/0x3b0
[   66.966967]  ksys_read+0x50/0xc0
[   66.966968]  do_syscall_64+0x38/0xe0
[   66.966971]  entry_SYSCALL_64_after_hwframe+0x4b/0x53
[   66.966972] RIP: 0033:0x7fcdd4814072

this is lctl get_param racing with mount command