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 lets 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 ]—

Weakness

The product calls free() twice on the same memory address.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/16852eccbdfaf41a666705e3f8be55cf2864c5ca
• https://git.kernel.org/stable/c/2935e556850e9c94d7a00adf14d3cd7fe406ac03
• https://git.kernel.org/stable/c/7ce9bb0b95fc280e9212b8922590c492ca1d9c39
• https://git.kernel.org/stable/c/86f3dcd1f331cfd4fd7ec88906955134ec51afbe
• https://git.kernel.org/stable/c/a351ff6b8ecca4229afaa0d98042bead8de64799
• https://git.kernel.org/stable/c/f8069f34c4c976786ded97498012225af87435d7