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mounting cifs share causes Oops - kernel NULL pointer dereference

This document (000021507) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15 SP6

Situation

After updating SP6 to kernel: 6.4.0-150600.23.7.3 or 6.4.0-150600.23.14.2 and mounting CIFS shares, the system hangs. 
 
Relevant parts of the traces could look like this:
[ xxxxxx] CIFS: Attempting to mount //<IP>/cifs/share/
[ xxxxxx ] CPU: 1 PID: 2859 Comm: ls Kdump: loaded Not tainted 6.4.0-150600.23.7-default #1 SLE15-SP6 ebc78bee233b1d2a183a14ef789e85be8041f896

[....]

[ xxxxxxx ] Krnl PSW : 0704e00180000000 000003ff8047caec (open_cached_dir+0x104/0x9c8 [cifs])
[ xxxxxxx ] Call Trace:
[ xxxxxxx ] [<000003ff8047caec>] open_cached_dir+0x104/0x9c8 [cifs]
[ xxxxxxx ] ([<000003ff8047ca9e>] open_cached_dir+0xb6/0x9c8 [cifs])
[ xxxxxxx ] [<000003ff804821f2>] cifs_readdir+0xab2/0x10c0 [cifs]

or

[ xxxxxxx ] CIFS: Attempting to mount //<IP>/cifs/share
[ xxxxxxx ] Unable to handle kernel pointer dereference in virtual kernel address space
...
[ xxxxxxx ] Oops: 0004 ilc:3 [#1] SMP

or 

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0 
Oops: 0000 [#1] PREEMPT SMP NOPTI
...
Call Trace:
? __die_body+0x1a/0x60
? page_fault_oops+0x131/0x510
? exc_page_fault+0x69/0x150
? asm_exc_page_fault+0x22/0x30
? strcmp+0x4/0x30
open_cached_dir+0x12f/0x9c0 [cifs 4bf515fd55be272b2b7f62ea07ad9bc4798fcc2f]

Resolution

The kernel update to version 6.4.0-150600.23.17.1 released August/2024 includes the patch to resolve the problem. 

Cause

The cause of the issue is some missing spin_unlock() calls in open_cached_dir() which were omitted in a backported patch.

Status

Reported to Engineering

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:000021507
  • Creation Date: 25-Jul-2024
  • Modified Date:15-Aug-2024
    • SUSE Linux Enterprise Server

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