[PATCH v1] i2c: qcom-geni: Clear stale TX/RX buffer pointers after GPI cleanup

[PATCH v1] i2c: qcom-geni: Clear stale TX/RX buffer pointers after GPI cleanup

[Aniket Randive]

The TX and RX buffer pointers are reused across messages in a GPI
transfer. After a buffer is unmapped and freed, the pointer is left
unchanged. A later message can reuse the stale pointer in the cleanup
path, causing a double unmap and double free.

This can happen when a READ message is followed by a WRITE message,
leaving a stale RX buffer pointer behind. A similar issue can occur for
the TX buffer when a mapping or allocation failure prevents the pointer
from being updated before the error path runs.

Clear tx_buf and rx_buf after unmapping and freeing them. This ensures
later iterations and error paths only see a valid buffer pointer or
NULL, preventing double unmap and double free issues.

Signed-off-by: Aniket Randive <aniket.randive@oss.qualcomm.com>
---
 drivers/i2c/busses/i2c-qcom-geni.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 942cfeee99ba..4965872b47d5 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -911,10 +911,13 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
 			goto err;
 		}
 
-		if (!gi2c->is_tx_multi_desc_xfer)
+		if (!gi2c->is_tx_multi_desc_xfer) {
 			geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
-		else if (tx_multi_xfer->unmap_msg_cnt != tx_multi_xfer->irq_cnt)
+			tx_buf = NULL;
+			rx_buf = NULL;
+		} else if (tx_multi_xfer->unmap_msg_cnt != tx_multi_xfer->irq_cnt) {
 			geni_i2c_gpi_multi_desc_unmap(gi2c, msgs, &peripheral);
+		}
 	}
 
 	return num;

---
base-commit: 89c07d98716a13454ec3fd9f97689e812cc71bd4
change-id: 20260901-i2c_double_free-09ab0b97e61d

Best regards,
--  
Aniket Randive <aniket.randive@oss.qualcomm.com>

Re: [PATCH v1] i2c: qcom-geni: Clear stale TX/RX buffer pointers after GPI cleanup

[Praveen Talari]

Hi

On 02-09-2026 20:15, Aniket Randive wrote:
> The TX and RX buffer pointers are reused across messages in a GPI
> transfer. After a buffer is unmapped and freed, the pointer is left
> unchanged. A later message can reuse the stale pointer in the cleanup
> path, causing a double unmap and double free.
>
> This can happen when a READ message is followed by a WRITE message,
> leaving a stale RX buffer pointer behind. A similar issue can occur for
> the TX buffer when a mapping or allocation failure prevents the pointer
> from being updated before the error path runs.
>
> Clear tx_buf and rx_buf after unmapping and freeing them. This ensures
> later iterations and error paths only see a valid buffer pointer or
> NULL, preventing double unmap and double free issues.
>
> Signed-off-by: Aniket Randive <aniket.randive@oss.qualcomm.com>
> ---
>   drivers/i2c/busses/i2c-qcom-geni.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
> index 942cfeee99ba..4965872b47d5 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -911,10 +911,13 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>   			goto err;
>   		}
>   
> -		if (!gi2c->is_tx_multi_desc_xfer)
> +		if (!gi2c->is_tx_multi_desc_xfer) {
>   			geni_i2c_gpi_unmap(gi2c, &msgs[i], tx_buf, tx_addr, rx_buf, rx_addr);
> -		else if (tx_multi_xfer->unmap_msg_cnt != tx_multi_xfer->irq_cnt)
> +			tx_buf = NULL;
> +			rx_buf = NULL;
> +		} else if (tx_multi_xfer->unmap_msg_cnt != tx_multi_xfer->irq_cnt) {
>   			geni_i2c_gpi_multi_desc_unmap(gi2c, msgs, &peripheral);
> +		}
>   	}
>   

Reviewed-by: Praveen Talari <praveen.talari@oss.qualcomm.com>


Thanks,

Praveen Talari

>   	return num;
>
> ---
> base-commit: 89c07d98716a13454ec3fd9f97689e812cc71bd4
> change-id: 20260901-i2c_double_free-09ab0b97e61d
>
> Best regards,
> --
> Aniket Randive <aniket.randive@oss.qualcomm.com>
>
>