[PATCH 4.19 64/88] firewire: remove check of list iterator against head past the loop body

Greg Kroah-Hartman
2022-05-10T13:40:03Z

From: Jakob Koschel <jakobkoschel@gmail.com>

commit 9423973869bd4632ffe669f950510c49296656e0 upstream.

When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.

While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Cc: <stable@vger.kernel.org>
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20220409041243.603210-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/firewire/core-transaction.c | 30 ++++++++++++++++--------------
drivers/firewire/sbp2.c | 13 +++++++------
2 files changed, 23 insertions(+), 20 deletions(-)

--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -86,24 +86,25 @@ static int try_cancel_split_timeout(stru
static int close_transaction(struct fw_transaction *transaction,
struct fw_card *card, int rcode)
{
- struct fw_transaction *t;
+ struct fw_transaction *t = NULL, *iter;
unsigned long flags;

spin_lock_irqsave(&card->lock, flags);
- list_for_each_entry(t, &card->transaction_list, link) {
- if (t == transaction) {
- if (!try_cancel_split_timeout(t)) {
+ list_for_each_entry(iter, &card->transaction_list, link) {
+ if (iter == transaction) {
+ if (!try_cancel_split_timeout(iter)) {
spin_unlock_irqrestore(&card->lock, flags);
goto timed_out;
}
- list_del_init(&t->link);
- card->tlabel_mask &= ~(1ULL << t->tlabel);
+ list_del_init(&iter->link);
+ card->tlabel_mask &= ~(1ULL << iter->tlabel);
+ t = iter;
break;
}
}
spin_unlock_irqrestore(&card->lock, flags);

- if (&t->link != &card->transaction_list) {
+ if (t) {
t->callback(card, rcode, NULL, 0, t->callback_data);
return 0;
}
@@ -938,7 +939,7 @@ EXPORT_SYMBOL(fw_core_handle_request);

void fw_core_handle_response(struct fw_card *card, struct fw_packet *p)
{
- struct fw_transaction *t;
+ struct fw_transaction *t = NULL, *iter;
unsigned long flags;
u32 *data;
size_t data_length;
@@ -950,20 +951,21 @@ void fw_core_handle_response(struct fw_c
rcode = HEADER_GET_RCODE(p->header[1]);

spin_lock_irqsave(&card->lock, flags);
- list_for_each_entry(t, &card->transaction_list, link) {
- if (t->node_id == source && t->tlabel == tlabel) {
- if (!try_cancel_split_timeout(t)) {
+ list_for_each_entry(iter, &card->transaction_list, link) {
+ if (iter->node_id == source && iter->tlabel == tlabel) {
+ if (!try_cancel_split_timeout(iter)) {
spin_unlock_irqrestore(&card->lock, flags);
goto timed_out;
}
- list_del_init(&t->link);
- card->tlabel_mask &= ~(1ULL << t->tlabel);
+ list_del_init(&iter->link);
+ card->tlabel_mask &= ~(1ULL << iter->tlabel);
+ t = iter;
break;
}
}
spin_unlock_irqrestore(&card->lock, flags);

- if (&t->link == &card->transaction_list) {
+ if (!t) {
timed_out:
fw_notice(card, "unsolicited response (source %x, tlabel %x)\n",
source, tlabel);
--- a/drivers/firewire/sbp2.c
+++ b/drivers/firewire/sbp2.c
@@ -421,7 +421,7 @@ static void sbp2_status_write(struct fw_
void *payload, size_t length, void *callback_data)
{
struct sbp2_logical_unit *lu = callback_data;
- struct sbp2_orb *orb;
+ struct sbp2_orb *orb = NULL, *iter;
struct sbp2_status status;
unsigned long flags;

@@ -446,17 +446,18 @@ static void sbp2_status_write(struct fw_

/* Lookup the orb corresponding to this status write. */
spin_lock_irqsave(&lu->tgt->lock, flags);
- list_for_each_entry(orb, &lu->orb_list, link) {
+ list_for_each_entry(iter, &lu->orb_list, link) {
if (STATUS_GET_ORB_HIGH(status) == 0 &&
- STATUS_GET_ORB_LOW(status) == orb->request_bus) {
- orb->rcode = RCODE_COMPLETE;
- list_del(&orb->link);
+ STATUS_GET_ORB_LOW(status) == iter->request_bus) {
+ iter->rcode = RCODE_COMPLETE;
+ list_del(&iter->link);
+ orb = iter;
break;
}
}
spin_unlock_irqrestore(&lu->tgt->lock, flags);

- if (&orb->link != &lu->orb_list) {
+ if (orb) {
orb->callback(orb, &status);
kref_put(&orb->kref, free_orb); /* orb callback reference */
} else {