CVE-2025-38593 — Bluetooth: hci_sync: fix double free in 'hci_discovery_filter_clear()'

Affected: Linux

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 [ ]…

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CVE-2025-38593 — Bluetooth: hci_sync: fix double free in 'hci_discovery_filter_clear()'