linux-kernel - [PATCH] dma: at_xdmac: fix a missing check on list iterator

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Message-Id: <20220327061154.4867-1-xiam0nd.tong@gmail.com>
Date:   Sun, 27 Mar 2022 14:11:54 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     ludovic.desroches@...rochip.com
Cc:     tudor.ambarus@...rochip.com, vkoul@...nel.org,
        linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Xiaomeng Tong <xiam0nd.tong@...il.com>, stable@...r.kernel.org
Subject: [PATCH] dma: at_xdmac: fix a missing check on list iterator

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@...r.kernel.org
Fixes: 82e2424635f4c ("dmaengine: xdmac: fix print warning on dma_addr_t variable")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
---
 drivers/dma/at_xdmac.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 1476156af74b..def564d1e8fa 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -1453,7 +1453,7 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 {
 	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;
@@ -1568,11 +1568,13 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 	 * 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;
 
-- 
2.17.1