cve/published/2025/CVE-2025-21673.mbox

From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: <linux-cve-announce@vger.kernel.org>
Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
Subject: CVE-2025-21673: smb: client: fix double free of TCP_Server_Info::hostname

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix double free of TCP_Server_Info::hostname

When shutting down the server in cifs_put_tcp_session(), cifsd thread
might be reconnecting to multiple DFS targets before it realizes it
should exit the loop, so @server->hostname can't be freed as long as
cifsd thread isn't done.  Otherwise the following can happen:

  RIP: 0010:__slab_free+0x223/0x3c0
  Code: 5e 41 5f c3 cc cc cc cc 4c 89 de 4c 89 cf 44 89 44 24 08 4c 89
  1c 24 e8 fb cf 8e 00 44 8b 44 24 08 4c 8b 1c 24 e9 5f fe ff ff <0f>
  0b 41 f7 45 08 00 0d 21 00 0f 85 2d ff ff ff e9 1f ff ff ff 80
  RSP: 0018:ffffb26180dbfd08 EFLAGS: 00010246
  RAX: ffff8ea34728e510 RBX: ffff8ea34728e500 RCX: 0000000000800068
  RDX: 0000000000800068 RSI: 0000000000000000 RDI: ffff8ea340042400
  RBP: ffffe112041ca380 R08: 0000000000000001 R09: 0000000000000000
  R10: 6170732e31303000 R11: 70726f632e786563 R12: ffff8ea34728e500
  R13: ffff8ea340042400 R14: ffff8ea34728e500 R15: 0000000000800068
  FS: 0000000000000000(0000) GS:ffff8ea66fd80000(0000)
  000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007ffc25376080 CR3: 000000012a2ba001 CR4:
  PKRU: 55555554
  Call Trace:
   <TASK>
   ? show_trace_log_lvl+0x1c4/0x2df
   ? show_trace_log_lvl+0x1c4/0x2df
   ? __reconnect_target_unlocked+0x3e/0x160 [cifs]
   ? __die_body.cold+0x8/0xd
   ? die+0x2b/0x50
   ? do_trap+0xce/0x120
   ? __slab_free+0x223/0x3c0
   ? do_error_trap+0x65/0x80
   ? __slab_free+0x223/0x3c0
   ? exc_invalid_op+0x4e/0x70
   ? __slab_free+0x223/0x3c0
   ? asm_exc_invalid_op+0x16/0x20
   ? __slab_free+0x223/0x3c0
   ? extract_hostname+0x5c/0xa0 [cifs]
   ? extract_hostname+0x5c/0xa0 [cifs]
   ? __kmalloc+0x4b/0x140
   __reconnect_target_unlocked+0x3e/0x160 [cifs]
   reconnect_dfs_server+0x145/0x430 [cifs]
   cifs_handle_standard+0x1ad/0x1d0 [cifs]
   cifs_demultiplex_thread+0x592/0x730 [cifs]
   ? __pfx_cifs_demultiplex_thread+0x10/0x10 [cifs]
   kthread+0xdd/0x100
   ? __pfx_kthread+0x10/0x10
   ret_from_fork+0x29/0x50
   </TASK>

The Linux kernel CVE team has assigned CVE-2025-21673 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.16 with commit 7be3248f313930ff3d3436d4e9ddbe9fccc1f541 and fixed in 6.6.74 with commit 1ea68070338518a1d31ce71e6abfe1b30001b27a
	Issue introduced in 5.16 with commit 7be3248f313930ff3d3436d4e9ddbe9fccc1f541 and fixed in 6.12.11 with commit a2be5f2ba34d0c6d5ef2624b24e3d852561fcd6a
	Issue introduced in 5.16 with commit 7be3248f313930ff3d3436d4e9ddbe9fccc1f541 and fixed in 6.13 with commit fa2f9906a7b333ba757a7dbae0713d8a5396186e
	Issue introduced in 5.14.19 with commit 49f933bb3016269dc50074eac5f6033d127644f1
	Issue introduced in 5.15.3 with commit 1c35a216ef77db708178ca225d796271f2f60a7a

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-21673
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/smb/client/connect.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/1ea68070338518a1d31ce71e6abfe1b30001b27a
	https://git.kernel.org/stable/c/a2be5f2ba34d0c6d5ef2624b24e3d852561fcd6a
	https://git.kernel.org/stable/c/fa2f9906a7b333ba757a7dbae0713d8a5396186e