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    Subject[PATCH 4.9 16/24] dma: at_xdmac: fix a missing check on list iterator
    Date
    From: Xiaomeng Tong <xiam0nd.tong@gmail.com>

    commit 206680c4e46b62fd8909385e0874a36952595b85 upstream.

    The bug is here:
    __func__, desc, &desc->tx_dma_desc.phys, ret, cookie, residue);

    The list iterator 'desc' will point to a bogus position containing
    HEAD if the list is empty or no element is found. To avoid dev_dbg()
    prints a invalid address, use a new variable 'iter' as the list
    iterator, while use the origin variable 'desc' as a dedicated
    pointer to point to the found element.

    Cc: stable@vger.kernel.org
    Fixes: 82e2424635f4c ("dmaengine: xdmac: fix print warning on dma_addr_t variable")
    Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
    Link: https://lore.kernel.org/r/20220327061154.4867-1-xiam0nd.tong@gmail.com
    Signed-off-by: Vinod Koul <vkoul@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/dma/at_xdmac.c | 12 +++++++-----
    1 file changed, 7 insertions(+), 5 deletions(-)

    --- a/drivers/dma/at_xdmac.c
    +++ b/drivers/dma/at_xdmac.c
    @@ -1392,7 +1392,7 @@ at_xdmac_tx_status(struct dma_chan *chan
    {
    struct at_xdmac_chan *atchan = to_at_xdmac_chan(chan);
    struct at_xdmac *atxdmac = to_at_xdmac(atchan->chan.device);
    - struct at_xdmac_desc *desc, *_desc;
    + struct at_xdmac_desc *desc, *_desc, *iter;
    struct list_head *descs_list;
    enum dma_status ret;
    int residue, retry;
    @@ -1507,11 +1507,13 @@ at_xdmac_tx_status(struct dma_chan *chan
    * microblock.
    */
    descs_list = &desc->descs_list;
    - list_for_each_entry_safe(desc, _desc, descs_list, desc_node) {
    - dwidth = at_xdmac_get_dwidth(desc->lld.mbr_cfg);
    - residue -= (desc->lld.mbr_ubc & 0xffffff) << dwidth;
    - if ((desc->lld.mbr_nda & 0xfffffffc) == cur_nda)
    + list_for_each_entry_safe(iter, _desc, descs_list, desc_node) {
    + dwidth = at_xdmac_get_dwidth(iter->lld.mbr_cfg);
    + residue -= (iter->lld.mbr_ubc & 0xffffff) << dwidth;
    + if ((iter->lld.mbr_nda & 0xfffffffc) == cur_nda) {
    + desc = iter;
    break;
    + }
    }
    residue += cur_ubc << dwidth;


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