linux-cve-announce - CVE-2025-38593: Bluetooth: hci_sync: fix double free in 'hci_discovery_filter

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Message-ID: <2025081918-CVE-2025-38593-22c2@gregkh>
Date: Tue, 19 Aug 2025 19:18:39 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38593: Bluetooth: hci_sync: fix double free in 'hci_discovery_filter_clear()'

From: Greg Kroah-Hartman <gregkh@...nel.org>

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

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

Bluetooth: hci_sync: fix double free in 'hci_discovery_filter_clear()'

Function 'hci_discovery_filter_clear()' frees 'uuids' array and then
sets it to NULL. There is a tiny chance of the following race:

'hci_cmd_sync_work()'

 'update_passive_scan_sync()'

   'hci_update_passive_scan_sync()'

     'hci_discovery_filter_clear()'
       kfree(uuids);

       <-------------------------preempted-------------------------------->
                                           'start_service_discovery()'

                                             'hci_discovery_filter_clear()'
                                               kfree(uuids); // DOUBLE FREE

       <-------------------------preempted-------------------------------->

      uuids = NULL;

To fix it let's add locking around 'kfree()' call and NULL pointer
assignment. Otherwise the following backtrace fires:

[ ] ------------[ cut here ]------------
[ ] kernel BUG at mm/slub.c:547!
[ ] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
[ ] CPU: 3 UID: 0 PID: 246 Comm: bluetoothd Tainted: G O 6.12.19-kernel #1
[ ] Tainted: [O]=OOT_MODULE
[ ] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ ] pc : __slab_free+0xf8/0x348
[ ] lr : __slab_free+0x48/0x348
...
[ ] Call trace:
[ ]  __slab_free+0xf8/0x348
[ ]  kfree+0x164/0x27c
[ ]  start_service_discovery+0x1d0/0x2c0
[ ]  hci_sock_sendmsg+0x518/0x924
[ ]  __sock_sendmsg+0x54/0x60
[ ]  sock_write_iter+0x98/0xf8
[ ]  do_iter_readv_writev+0xe4/0x1c8
[ ]  vfs_writev+0x128/0x2b0
[ ]  do_writev+0xfc/0x118
[ ]  __arm64_sys_writev+0x20/0x2c
[ ]  invoke_syscall+0x68/0xf0
[ ]  el0_svc_common.constprop.0+0x40/0xe0
[ ]  do_el0_svc+0x1c/0x28
[ ]  el0_svc+0x30/0xd0
[ ]  el0t_64_sync_handler+0x100/0x12c
[ ]  el0t_64_sync+0x194/0x198
[ ] Code: 8b0002e6 eb17031f 54fffbe1 d503201f (d4210000)
[ ] ---[ end trace 0000000000000000 ]---

The Linux kernel CVE team has assigned CVE-2025-38593 to this issue.


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

	Issue introduced in 5.17 with commit ad383c2c65a5baf16e334cd40a013cc302176891 and fixed in 6.12.42 with commit 16852eccbdfaf41a666705e3f8be55cf2864c5ca
	Issue introduced in 5.17 with commit ad383c2c65a5baf16e334cd40a013cc302176891 and fixed in 6.15.10 with commit a351ff6b8ecca4229afaa0d98042bead8de64799
	Issue introduced in 5.17 with commit ad383c2c65a5baf16e334cd40a013cc302176891 and fixed in 6.16.1 with commit f8069f34c4c976786ded97498012225af87435d7
	Issue introduced in 5.17 with commit ad383c2c65a5baf16e334cd40a013cc302176891 and fixed in 6.17-rc1 with commit 2935e556850e9c94d7a00adf14d3cd7fe406ac03

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-2025-38593
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:
	include/net/bluetooth/hci_core.h


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/16852eccbdfaf41a666705e3f8be55cf2864c5ca
	https://git.kernel.org/stable/c/a351ff6b8ecca4229afaa0d98042bead8de64799
	https://git.kernel.org/stable/c/f8069f34c4c976786ded97498012225af87435d7
	https://git.kernel.org/stable/c/2935e556850e9c94d7a00adf14d3cd7fe406ac03