[PATCH] dmaengine: ti: k3-udma: Fix NULL pointer dereference error

[Kishon Vijay Abraham I]

bcdma_get_*() and udma_get_*() checks if bchan/rchan/tchan/rflow is
already allocated by checking if it has a NON NULL value. For the
error cases, bchan/rchan/tchan/rflow will have error value
and bcdma_get_*() and udma_get_*() considers this as already allocated
(PASS) since the error values are NON NULL. This results in
NULL pointer dereference error while de-referencing
bchan/rchan/tchan/rflow.

Reset the value of bchan/rchan/tchan/rflow to NULL if the allocation
actually fails.

Fixes: 017794739702 ("dmaengine: ti: k3-udma: Initial support for K3 BCDMA")
Fixes: 25dcb5dd7b7c ("dmaengine: ti: New driver for K3 UDMA")
Signed-off-by: Kishon Vijay Abraham I <kis...@ti.com>
---
 drivers/dma/ti/k3-udma.c | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
index 298460438bb4..aa4ef583ff83 100644
--- a/drivers/dma/ti/k3-udma.c
+++ b/drivers/dma/ti/k3-udma.c
@@ -1330,6 +1330,7 @@ static int bcdma_get_bchan(struct udma_chan *uc)
 {
        struct udma_dev *ud = uc->ud;
        enum udma_tp_level tpl;
+       int ret;
 
        if (uc->bchan) {
                dev_dbg(ud->dev, "chan%d: already have bchan%d allocated\n",
@@ -1347,8 +1348,11 @@ static int bcdma_get_bchan(struct udma_chan *uc)
                tpl = ud->bchan_tpl.levels - 1;
 
        uc->bchan = __udma_reserve_bchan(ud, tpl, -1);
-       if (IS_ERR(uc->bchan))
-               return PTR_ERR(uc->bchan);
+       if (IS_ERR(uc->bchan)) {
+               ret = PTR_ERR(uc->bchan);
+               uc->bchan = NULL;
+               return ret;
+       }
 
        uc->tchan = uc->bchan;
 
@@ -1358,6 +1362,7 @@ static int bcdma_get_bchan(struct udma_chan *uc)
 static int udma_get_tchan(struct udma_chan *uc)
 {
        struct udma_dev *ud = uc->ud;
+       int ret;
 
        if (uc->tchan) {
                dev_dbg(ud->dev, "chan%d: already have tchan%d allocated\n",
@@ -1372,8 +1377,11 @@ static int udma_get_tchan(struct udma_chan *uc)
         */
        uc->tchan = __udma_reserve_tchan(ud, uc->config.channel_tpl,
                                         uc->config.mapped_channel_id);
-       if (IS_ERR(uc->tchan))
-               return PTR_ERR(uc->tchan);
+       if (IS_ERR(uc->tchan)) {
+               ret = PTR_ERR(uc->tchan);
+               uc->tchan = NULL;
+               return ret;
+       }
 
        if (ud->tflow_cnt) {
                int tflow_id;
@@ -1403,6 +1411,7 @@ static int udma_get_tchan(struct udma_chan *uc)
 static int udma_get_rchan(struct udma_chan *uc)
 {
        struct udma_dev *ud = uc->ud;
+       int ret;
 
        if (uc->rchan) {
                dev_dbg(ud->dev, "chan%d: already have rchan%d allocated\n",
@@ -1417,8 +1426,13 @@ static int udma_get_rchan(struct udma_chan *uc)
         */
        uc->rchan = __udma_reserve_rchan(ud, uc->config.channel_tpl,
                                         uc->config.mapped_channel_id);
+       if (IS_ERR(uc->rchan)) {
+               ret = PTR_ERR(uc->rchan);
+               uc->rchan = NULL;
+               return ret;
+       }
 
-       return PTR_ERR_OR_ZERO(uc->rchan);
+       return 0;
 }
 
 static int udma_get_chan_pair(struct udma_chan *uc)
@@ -1472,6 +1486,7 @@ static int udma_get_chan_pair(struct udma_chan *uc)
 static int udma_get_rflow(struct udma_chan *uc, int flow_id)
 {
        struct udma_dev *ud = uc->ud;
+       int ret;
 
        if (!uc->rchan) {
                dev_err(ud->dev, "chan%d: does not have rchan??\n", uc->id);
@@ -1485,6 +1500,11 @@ static int udma_get_rflow(struct udma_chan *uc, int 
flow_id)
        }
 
        uc->rflow = __udma_get_rflow(ud, flow_id);
+       if (IS_ERR(uc->rflow)) {
+               ret = PTR_ERR(uc->rflow);
+               uc->rflow = NULL;
+               return ret;
+       }
 
        return PTR_ERR_OR_ZERO(uc->rflow);
 }
-- 
2.17.1