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    Subject[PATCH 5.17 025/140] firewire: remove check of list iterator against head past the loop body
    Date
    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
    @@ -73,24 +73,25 @@ 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;
    }
    @@ -935,7 +936,7 @@ 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;
    @@ -947,20 +948,21 @@ 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
    @@ -408,7 +408,7 @@ 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;

    @@ -433,17 +433,18 @@ 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 {

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