Hello, I'd like to report a regression in firewire-ohci that results in the kernel hardlocking when re-discovering a FireWire device. TI XIO2213B RME FireFace 800 It will occur under three conditions: * power-cycling the FireWire device * un- and re-plugging the FireWire device * suspending and then waking the PC Often it would also occur directly on boot in QEMU but I have not yet observed this specific behavior on bare metal. Here is an excerpt from the stack trace (don't know whether it is acceptable to send in full): kernel: ------------[ cut here ]------------ kernel: refcount_t: addition on 0; use-after-free. kernel: WARNING: CPU: 3 PID: 116 at lib/refcount.c:25 refcount_warn_saturate (/build/linux/lib/refcount.c:25 (discriminator 1)) kernel: Workqueue: firewire_ohci bus_reset_work kernel: RIP: 0010:refcount_warn_saturate (/build/linux/lib/refcount.c:25 (discriminator 1)) kernel: Call Trace: kernel: <TASK> kernel: ? refcount_warn_saturate (/build/linux/lib/refcount.c:25 (discriminator 1)) kernel: ? __warn.cold (/build/linux/kernel/panic.c:693) kernel: ? refcount_warn_saturate (/build/linux/lib/refcount.c:25 (discriminator 1)) kernel: ? report_bug (/build/linux/lib/bug.c:180 /build/linux/lib/bug.c:219) kernel: ? handle_bug (/build/linux/arch/x86/kernel/traps.c:218) kernel: ? exc_invalid_op (/build/linux/arch/x86/kernel/traps.c:260 (discriminator 1)) kernel: ? asm_exc_invalid_op (/build/linux/./arch/x86/include/asm/idtentry.h:621) kernel: ? refcount_warn_saturate (/build/linux/lib/refcount.c:25 (discriminator 1)) kernel: for_each_fw_node (/build/linux/./include/linux/refcount.h:190 /build/linux/./include/linux/refcount.h:241 /build/linux/./include/linux/refcount.h:258 /build/linux/drivers/firewire/core.h:199 /build/linux/drivers/firewire/core-topology.c:275) kernel: ? __pfx_report_found_node (/build/linux/drivers/firewire/core- topology.c:312) kernel: fw_core_handle_bus_reset (/build/linux/drivers/firewire/core- topology.c:399 (discriminator 1) /build/linux/drivers/firewire/core- topology.c:504 (discriminator 1)) kernel: bus_reset_work (/build/linux/drivers/firewire/ohci.c:2121) kernel: process_one_work (/build/linux/./arch/x86/include/asm/jump_label.h:27 /build/linux/./include/linux/jump_label.h:207 /build/linux/./include/trace/events/workqueue.h:110 /build/linux/kernel/workqueue.c:3236) kernel: worker_thread (/build/linux/kernel/workqueue.c:3306 (discriminator 2) /build/linux/kernel/workqueue.c:3393 (discriminator 2)) kernel: ? __pfx_worker_thread (/build/linux/kernel/workqueue.c:3339) kernel: kthread (/build/linux/kernel/kthread.c:389) kernel: ? __pfx_kthread (/build/linux/kernel/kthread.c:342) kernel: ret_from_fork (/build/linux/arch/x86/kernel/process.c:153) kernel: ? __pfx_kthread (/build/linux/kernel/kthread.c:342) kernel: ret_from_fork_asm (/build/linux/arch/x86/entry/entry_64.S:254) kernel: </TASK> I have identified the commit via bisection: 24b7f8e5cd656196a13077e160aec45ad89b58d9 firewire: core: use helper functions for self ID sequence It was part of the following patch series: firewire: add tracepoints events for self ID sequence https://lore.kernel.org/all/20240605235155.116468-6-o-takashi@xxxxxxxxxxxxx/ #regzbot introduced: 24b7f8e5cd65 Since this was before v6.10-rc5 and stable 6.10.14 is EOL, stable v6.11.5 and mainline are affected. Reversion appears to be non-trivial as it is part of a patch series, other files have been altered as well and other commits build on top of it. Call chain: core-topology.c fw_core_handle_bus_reset() -> core-topology.c for_each_fw_node(card, local_node, report_found_node) -> core.h fw_node_get(root) -> refcount.h __refcount_inc(&node) -> refcount.h __refcount_add(1, r, oldp); -> refcount.h refcount_warn_saturate(r, REFCOUNT_ADD_UAF); -> refcount.h REFCOUNT_WARN("addition on 0; use-after-free") Since local_node of fw_core_handle_bus_reset() is retrieved by local_node = build_tree(card, self_ids, self_id_count); build_tree() needs to be looked at, it was indeed altered by 24b7f8e5cd65. After a hard 3 hour look traversing all used functions and comparing against the original function (as of e404cacfc5ed), this caught my eye: for (port_index = 0; port_index < total_port_count; ++port_index) { switch (port_status) { case PHY_PACKET_SELF_ID_PORT_STATUS_PARENT: node->color = i; In both for loops, "port_index" was replaced by "i" "i" remains in use above: for (i = 0, h = &stack; i < child_port_count; i++) h = h->prev; While the original also used the less descriptive i in the loop for (i = 0; i < port_count; i++) { switch (get_port_type(sid, i)) { case SELFID_PORT_PARENT: node->color = i; but reset it to 0 at the beginning of the loop. So the stray "i" in the for loop should be replaced with the loop iterator "port_index" as it is meant to be synchronous with the loop iterator (i.e. the port_index), no? diff --git a/drivers/firewire/core-topology.c b/drivers/firewire/core- topology.c index 8c10f47cc8fc..7fd91ba9c9c4 100644 --- a/drivers/firewire/core-topology.c +++ b/drivers/firewire/core-topology.c @@ -207,7 +207,7 @@ static struct fw_node *build_tree(struct fw_card *card, const u32 *sid, int self // the node->ports array where the parent node should be. Later, // when we handle the parent node, we fix up the reference. ++parent_count; - node->color = i; + node->color = port_index; break; What threw me off was discaridng node->color as it would be replaced later anyways (can't be important!), or so I thought. Please tell me, is this line of reasoning correct or am I missing something? Compiling 24b7f8e5cd65 and later mainline with the patch above resulted in a kernel that didn't crash! In case my solution should turn out to be correct, I will gladly submit the patch. Kind regards, Edmund Raile.
