[4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0

[Dave Chinner]

Hi folks,

Just updated my test boxes from 4.9 to a current Linus 4.10 merge
window kernel to test the XFS merge I am preparing for Linus.
Unfortunately, all my test VMs using iscsi failed pretty much
instantly on the first mount of an iscsi device:

[  159.372704] XFS (sdb): EXPERIMENTAL reverse mapping btree feature enabled. Use at your own risk!
[  159.374612] XFS (sdb): Mounting V5 Filesystem
[  159.425710] XFS (sdb): Ending clean mount
[  160.274438] BUG: unable to handle kernel NULL pointer dereference at 000000000000000c
[  160.275851] IP: iscsi_tcp_segment_done+0x20d/0x2e0
[  160.276565] PGD 336ed067 [  160.276885] PUD 31b0d067
PMD 0 [  160.277309]
[  160.277523] Oops: 0000 [#1] PREEMPT SMP
[  160.278004] Modules linked in:
[  160.278407] CPU: 0 PID: 16 Comm: kworker/u2:1 Not tainted 4.9.0-dgc #18
[  160.279224] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[  160.280314] Workqueue: iscsi_q_2 iscsi_xmitworker
[  160.280919] task: ffff88003e280000 task.stack: ffffc90000080000
[  160.281647] RIP: 0010:iscsi_tcp_segment_done+0x20d/0x2e0
[  160.282312] RSP: 0018:ffffc90000083c38 EFLAGS: 00010206
[  160.282980] RAX: 0000000000000000 RBX: ffff880039061730 RCX: 0000000000000000
[  160.283854] RDX: 0000000000001e00 RSI: 0000000000000000 RDI: ffff880039061730
[  160.284738] RBP: ffffc90000083c90 R08: 0000000000000200 R09: 00000000000005a8
[  160.285627] R10: 000000009835607d R11: 0000000000000000 R12: 0000000000000200
[  160.286495] R13: 0000000000000000 R14: ffff8800390615a0 R15: ffff880039061730
[  160.287362] FS:  0000000000000000(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000
[  160.288340] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  160.289113] CR2: 000000000000000c CR3: 0000000031a8d000 CR4: 00000000000006f0
[  160.290084] Call Trace:
[  160.290429]  ? inet_sendpage+0x4d/0x140
[  160.290957]  iscsi_sw_tcp_xmit_segment+0x89/0x110
[  160.291597]  iscsi_sw_tcp_pdu_xmit+0x56/0x180
[  160.292190]  iscsi_tcp_task_xmit+0xb8/0x280
[  160.292771]  iscsi_xmit_task+0x53/0xc0
[  160.293282]  iscsi_xmitworker+0x274/0x310
[  160.293835]  process_one_work+0x1de/0x4d0
[  160.294388]  worker_thread+0x4b/0x4f0
[  160.294889]  kthread+0x10c/0x140
[  160.295333]  ? process_one_work+0x4d0/0x4d0
[  160.295898]  ? kthread_create_on_node+0x40/0x40
[  160.296525]  ret_from_fork+0x25/0x30
[  160.297015] Code: 43 18 00 00 00 00 e9 ad fe ff ff 48 8b 7b 30 e8 da e7 ca ff 8b 53 10 44 89 ee 48 89 df 2b 53 14 48 89 43 30 c7 43 40 00 00 00 00 <8b
[  160.300674] RIP: iscsi_tcp_segment_done+0x20d/0x2e0 RSP: ffffc90000083c38
[  160.301584] CR2: 000000000000000c


Known problem, or something new?

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx