[PATCH v2] ata: dwc_460ex: Avoid potential NULL pointer dereference

From: Aditya Pakki
Date: Mon Mar 25 2019 - 18:55:00 EST


dma_async_tx_descriptor can contain a NULL variable and using
it in dmaengine_submit without checking can crash the process.
This patch avoids such a scenario.

Signed-off-by: Aditya Pakki <pakki001@xxxxxxx>

---
v1: Return error in case of failure to desc variable to avoid hang up.
---
drivers/ata/sata_dwc_460ex.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index 6f142aa54f5f..63d922c624a4 100644
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c
@@ -185,7 +185,7 @@ enum {
/*
* Prototypes
*/
-static void sata_dwc_bmdma_start_by_tag(struct ata_queued_cmd *qc, u8 tag);
+static int sata_dwc_bmdma_start_by_tag(struct ata_queued_cmd *qc, u8 tag);
static int sata_dwc_qc_complete(struct ata_port *ap, struct ata_queued_cmd *qc,
u32 check_status);
static void sata_dwc_dma_xfer_complete(struct ata_port *ap, u32 check_status);
@@ -512,7 +512,7 @@ static irqreturn_t sata_dwc_isr(int irq, void *dev_instance)
struct ata_queued_cmd *qc;
unsigned long flags;
u8 status, tag;
- int handled, num_processed, port = 0;
+ int handled, num_processed, ret, port = 0;
uint intpr, sactive, sactive2, tag_mask;
struct sata_dwc_device_port *hsdevp;
hsdev->sactive_issued = 0;
@@ -553,10 +553,11 @@ static irqreturn_t sata_dwc_isr(int irq, void *dev_instance)
* be completed.
*/
qc->ap->link.active_tag = tag;
- sata_dwc_bmdma_start_by_tag(qc, tag);
-
- handled = 1;
- goto DONE;
+ ret = sata_dwc_bmdma_start_by_tag(qc, tag);
+ if (!ret) {
+ handled = 1;
+ goto DONE;
+ }
}
sata_dwc_scr_read(&ap->link, SCR_ACTIVE, &sactive);
tag_mask = (hsdev->sactive_issued | sactive) ^ sactive;
@@ -1008,7 +1009,7 @@ static void sata_dwc_bmdma_setup(struct ata_queued_cmd *qc)
sata_dwc_bmdma_setup_by_tag(qc, tag);
}

-static void sata_dwc_bmdma_start_by_tag(struct ata_queued_cmd *qc, u8 tag)
+static int sata_dwc_bmdma_start_by_tag(struct ata_queued_cmd *qc, u8 tag)
{
int start_dma;
u32 reg;
@@ -1018,6 +1019,9 @@ static void sata_dwc_bmdma_start_by_tag(struct ata_queued_cmd *qc, u8 tag)
struct dma_async_tx_descriptor *desc = hsdevp->desc[tag];
int dir = qc->dma_dir;

+ if (!desc)
+ return -ENOMEM;
+
if (hsdevp->cmd_issued[tag] != SATA_DWC_CMD_ISSUED_NOT) {
start_dma = 1;
if (dir == DMA_TO_DEVICE)
@@ -1055,9 +1059,10 @@ static void sata_dwc_bmdma_start_by_tag(struct ata_queued_cmd *qc, u8 tag)
dmaengine_submit(desc);
dma_async_issue_pending(hsdevp->chan);
}
+ return 0;
}

-static void sata_dwc_bmdma_start(struct ata_queued_cmd *qc)
+static int sata_dwc_bmdma_start(struct ata_queued_cmd *qc)
{
u8 tag = qc->hw_tag;

@@ -1068,7 +1073,7 @@ static void sata_dwc_bmdma_start(struct ata_queued_cmd *qc)
tag = 0;
}
dev_dbg(qc->ap->dev, "%s\n", __func__);
- sata_dwc_bmdma_start_by_tag(qc, tag);
+ return sata_dwc_bmdma_start_by_tag(qc, tag);
}

static unsigned int sata_dwc_qc_issue(struct ata_queued_cmd *qc)
--
2.17.1