[PATCH 5.10 56/86] dma: at_xdmac: fix a missing check on list iterator

Greg Kroah-Hartman
2022-04-26T08:54:27Z

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
@@ -1390,7 +1390,7 @@ 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;
@@ -1505,11 +1505,13 @@ 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;