CVE-2025-38593

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 ]---