[PATCH net v5] net: stmmac: fix error path cleanup in DMA descriptor ring allocation

[PATCH net v5] net: stmmac: fix error path cleanup in DMA descriptor ring allocation

[Ding Hui]

From: Ding Hui <dinghui@lixiang.com>

__alloc_dma_rx_desc_resources() and __alloc_dma_tx_desc_resources()
allocate resources in multiple steps but return early on failure
without cleaning up what they have already allocated. The outer
error paths then call the free helpers on partially-initialized
queues, which dereference pointers that were never allocated:

  - dma_free_rx_skbufs() and dma_free_rx_xskbufs() dereference
    rx_q->buf_pool[i] via stmmac_free_rx_buffer(), but buf_pool
    may be NULL if its kzalloc_objs() failed.

  - dma_free_tx_skbufs() dereferences tx_q->tx_skbuff_dma[i] via
    stmmac_free_tx_buffer(), but tx_skbuff_dma may be NULL if its
    kzalloc_objs() failed.

  - stmmac_free_tx_buffer() dereferences tx_q->xdpf[i] and
    tx_q->tx_skbuff[i] (aliased through a union), but tx_skbuff
    may be NULL if its allocation failed while tx_skbuff_dma
    succeeded.

Fix this by making each allocation function responsible for undoing
its own allocations on error, following the standard kernel error
handling pattern of cleaning up in reverse order. Also add NULL
checks in the free helpers as a defensive measure, since they may
be called on partially-initialized queues.
Additionally, make __free_dma_rx_desc_resources() and
__free_dma_tx_desc_resources() clear the pointers they free, so that
the NULL guards in the free helpers hold reliably when the long-lived
priv->dma_conf is reused across XDP open/release cycles.
Free the RX resources in alloc_dma_desc_resources() when the TX
allocation fails, as the callers only free dma_conf itself on
that path.
After __stmmac_open() copies a temporary dma_conf into priv->dma_conf,
release the descriptor resources through priv->dma_conf on an open
failure. This keeps the long-lived configuration consistent with the
resource cleanup while callers only free the temporary container.
Finally, hold RTNL while descriptors_status inspects the descriptor
rings. This serializes the debugfs reader with control-plane resource
teardown paths and allows it to safely report queues whose descriptor
rings are not allocated. Skip queues whose descriptor rings are not
allocated in stmmac_rings_status_show() to avoid dereferencing a NULL
pointer.

Signed-off-by: Ding Hui <dinghui@lixiang.com>

---
Changes in v5:
  - Release copied descriptor resources through priv->dma_conf when
    __stmmac_open() fails, avoiding stale pointers in the long-lived
    configuration.
  - Hold RTNL while descriptors_status reads descriptor rings.
  - Correct the commit message to refer to descriptors_status as a
    debugfs entry rather than a sysfs entry.
  - Link to v4:
    https://lore.kernel.org/netdev/20261001035045.3305816-1-dinghui1111@163.com/
Changes in v4:
  - Free the RX resources in alloc_dma_desc_resources() when the TX
    allocation fails.
  - Skip queues whose descriptor rings are not allocated in
    stmmac_rings_status_show() and print a hint instead.
  - Link to v3:
    https://lore.kernel.org/netdev/20260919121436.1642724-1-dinghui1111@163.com/
Changes in v3:
  - Use addr directly in __alloc_dma_rx_desc_resources() error path
    instead of the if/else block on rx_q->dma_erx/dma_rx.
  - Clear the freed pointers in __free_dma_rx_desc_resources() and
    __free_dma_tx_desc_resources().
  - Link to v2:
    https://lore.kernel.org/netdev/20260905154654.1725313-1-dinghui1111@163.com/
Changes in v2:
  - Instead of only adding NULL checks in the free helpers, also fix
    __alloc_dma_rx_desc_resources() and __alloc_dma_tx_desc_resources()
    to clean up their own allocations on error, as suggested by Andrew.
  - Update commit message.
  - Link to v1:
    https://lore.kernel.org/netdev/20260830040610.1156008-1-dinghui1111@163.com/
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 112 +++++++++++++++---
 1 file changed, 96 insertions(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index f2fc89176654..852a8b103c45 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1728,7 +1728,7 @@ static void stmmac_free_tx_buffer(struct stmmac_priv *priv,
 					 DMA_TO_DEVICE);
 	}
 
-	if (tx_q->xdpf[i] &&
+	if (tx_q->xdpf && tx_q->xdpf[i] &&
 	    (tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_XDP_TX ||
 	     tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_XDP_NDO)) {
 		xdp_return_frame(tx_q->xdpf[i]);
@@ -1738,7 +1738,7 @@ static void stmmac_free_tx_buffer(struct stmmac_priv *priv,
 	if (tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_XSK_TX)
 		tx_q->xsk_frames_done++;
 
-	if (tx_q->tx_skbuff[i] &&
+	if (tx_q->tx_skbuff && tx_q->tx_skbuff[i] &&
 	    tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_SKB) {
 		dev_kfree_skb_any(tx_q->tx_skbuff[i]);
 		tx_q->tx_skbuff[i] = NULL;
@@ -1761,6 +1761,10 @@ static void dma_free_rx_skbufs(struct stmmac_priv *priv,
 	struct stmmac_rx_queue *rx_q = &dma_conf->rx_queue[queue];
 	int i;
 
+	/* buf_pool may not be allocated if alloc failed early */
+	if (!rx_q->buf_pool)
+		return;
+
 	for (i = 0; i < dma_conf->dma_rx_size; i++)
 		stmmac_free_rx_buffer(priv, rx_q, i);
 }
@@ -1802,6 +1806,10 @@ static void dma_free_rx_xskbufs(struct stmmac_priv *priv,
 	struct stmmac_rx_queue *rx_q = &dma_conf->rx_queue[queue];
 	int i;
 
+	/* buf_pool may not be allocated if alloc failed early */
+	if (!rx_q->buf_pool)
+		return;
+
 	for (i = 0; i < dma_conf->dma_rx_size; i++) {
 		struct stmmac_rx_buffer *buf = &rx_q->buf_pool[i];
 
@@ -2097,6 +2105,10 @@ static void dma_free_tx_skbufs(struct stmmac_priv *priv,
 	struct stmmac_tx_queue *tx_q = &dma_conf->tx_queue[queue];
 	int i;
 
+	/* tx_skbuff_dma may not be allocated if alloc failed early */
+	if (!tx_q->tx_skbuff_dma)
+		return;
+
 	tx_q->xsk_frames_done = 0;
 
 	for (i = 0; i < dma_conf->dma_tx_size; i++)
@@ -2154,13 +2166,20 @@ static void __free_dma_rx_desc_resources(struct stmmac_priv *priv,
 	size = stmmac_get_rx_desc_size(priv) * dma_conf->dma_rx_size;
 
 	dma_free_coherent(priv->device, size, addr, rx_q->dma_rx_phy);
+	rx_q->dma_erx = NULL;
+	rx_q->dma_rx = NULL;
+	rx_q->dma_rx_phy = 0;
 
 	if (xdp_rxq_info_is_reg(&rx_q->xdp_rxq))
 		xdp_rxq_info_unreg(&rx_q->xdp_rxq);
 
 	kfree(rx_q->buf_pool);
-	if (rx_q->page_pool)
+	rx_q->buf_pool = NULL;
+
+	if (rx_q->page_pool) {
 		page_pool_destroy(rx_q->page_pool);
+		rx_q->page_pool = NULL;
+	}
 }
 
 static void free_dma_rx_desc_resources(struct stmmac_priv *priv,
@@ -2202,9 +2221,16 @@ static void __free_dma_tx_desc_resources(struct stmmac_priv *priv,
 	size = stmmac_get_tx_desc_size(priv, tx_q) * dma_conf->dma_tx_size;
 
 	dma_free_coherent(priv->device, size, addr, tx_q->dma_tx_phy);
+	tx_q->dma_etx = NULL;
+	tx_q->dma_entx = NULL;
+	tx_q->dma_tx = NULL;
+	tx_q->dma_tx_phy = 0;
 
 	kfree(tx_q->tx_skbuff_dma);
+	tx_q->tx_skbuff_dma = NULL;
+
 	kfree(tx_q->tx_skbuff);
+	tx_q->tx_skbuff = NULL;
 }
 
 static void free_dma_tx_desc_resources(struct stmmac_priv *priv,
@@ -2272,15 +2298,19 @@ static int __alloc_dma_rx_desc_resources(struct stmmac_priv *priv,
 	}
 
 	rx_q->buf_pool = kzalloc_objs(*rx_q->buf_pool, dma_conf->dma_rx_size);
-	if (!rx_q->buf_pool)
-		return -ENOMEM;
+	if (!rx_q->buf_pool) {
+		ret = -ENOMEM;
+		goto err_destroy_pool;
+	}
 
 	size = stmmac_get_rx_desc_size(priv) * dma_conf->dma_rx_size;
 
 	addr = dma_alloc_coherent(priv->device, size, &rx_q->dma_rx_phy,
 				  GFP_KERNEL);
-	if (!addr)
-		return -ENOMEM;
+	if (!addr) {
+		ret = -ENOMEM;
+		goto err_free_buf_pool;
+	}
 
 	if (priv->extend_desc)
 		rx_q->dma_erx = addr;
@@ -2296,10 +2326,22 @@ static int __alloc_dma_rx_desc_resources(struct stmmac_priv *priv,
 	ret = xdp_rxq_info_reg(&rx_q->xdp_rxq, priv->dev, queue, napi_id);
 	if (ret) {
 		netdev_err(priv->dev, "Failed to register xdp rxq info\n");
-		return -EINVAL;
+		goto err_free_dma;
 	}
 
 	return 0;
+
+err_free_dma:
+	dma_free_coherent(priv->device, size, addr, rx_q->dma_rx_phy);
+	rx_q->dma_erx = NULL;
+	rx_q->dma_rx = NULL;
+err_free_buf_pool:
+	kfree(rx_q->buf_pool);
+	rx_q->buf_pool = NULL;
+err_destroy_pool:
+	page_pool_destroy(rx_q->page_pool);
+	rx_q->page_pool = NULL;
+	return ret;
 }
 
 static int alloc_dma_rx_desc_resources(struct stmmac_priv *priv,
@@ -2352,14 +2394,14 @@ static int __alloc_dma_tx_desc_resources(struct stmmac_priv *priv,
 
 	tx_q->tx_skbuff = kzalloc_objs(struct sk_buff *, dma_conf->dma_tx_size);
 	if (!tx_q->tx_skbuff)
-		return -ENOMEM;
+		goto err_free_skbuff_dma;
 
 	size = stmmac_get_tx_desc_size(priv, tx_q) * dma_conf->dma_tx_size;
 
 	addr = dma_alloc_coherent(priv->device, size,
 				  &tx_q->dma_tx_phy, GFP_KERNEL);
 	if (!addr)
-		return -ENOMEM;
+		goto err_free_skbuff;
 
 	if (priv->extend_desc)
 		tx_q->dma_etx = addr;
@@ -2369,6 +2411,14 @@ static int __alloc_dma_tx_desc_resources(struct stmmac_priv *priv,
 		tx_q->dma_tx = addr;
 
 	return 0;
+
+err_free_skbuff:
+	kfree(tx_q->tx_skbuff);
+	tx_q->tx_skbuff = NULL;
+err_free_skbuff_dma:
+	kfree(tx_q->tx_skbuff_dma);
+	tx_q->tx_skbuff_dma = NULL;
+	return -ENOMEM;
 }
 
 static int alloc_dma_tx_desc_resources(struct stmmac_priv *priv,
@@ -2411,6 +2461,8 @@ static int alloc_dma_desc_resources(struct stmmac_priv *priv,
 		return ret;
 
 	ret = alloc_dma_tx_desc_resources(priv, dma_conf);
+	if (ret)
+		free_dma_rx_desc_resources(priv, dma_conf);
 
 	return ret;
 }
@@ -4182,6 +4234,7 @@ static int __stmmac_open(struct net_device *dev,
 
 	stmmac_release_ptp(priv);
 init_error:
+	free_dma_desc_resources(priv, &priv->dma_conf);
 	return ret;
 }
 
@@ -4214,8 +4267,13 @@ static int stmmac_open(struct net_device *dev)
 	}
 
 	ret = __stmmac_open(dev, dma_conf);
-	if (ret)
-		goto err_serdes;
+	if (ret) {
+		stmmac_legacy_serdes_power_down(priv);
+		phylink_disconnect_phy(priv->phylink);
+		pm_runtime_put(priv->device);
+		kfree(dma_conf);
+		return ret;
+	}
 
 	kfree(dma_conf);
 
@@ -4224,8 +4282,6 @@ static int stmmac_open(struct net_device *dev)
 
 	return ret;
 
-err_serdes:
-	stmmac_legacy_serdes_power_down(priv);
 err_disconnect_phy:
 	phylink_disconnect_phy(priv->phylink);
 err_runtime_pm:
@@ -6130,7 +6186,6 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 
 		ret = __stmmac_open(dev, dma_conf);
 		if (ret) {
-			free_dma_desc_resources(priv, dma_conf);
 			kfree(dma_conf);
 			netdev_err(priv->dev, "failed reopening the interface after MTU change\n");
 			return ret;
@@ -6501,8 +6556,10 @@ static int stmmac_rings_status_show(struct seq_file *seq, void *v)
 	u8 tx_count = priv->plat->tx_queues_to_use;
 	u8 queue;
 
+	rtnl_lock();
+
 	if ((dev->flags & IFF_UP) == 0)
-		return 0;
+		goto out;
 
 	for (queue = 0; queue < rx_count; queue++) {
 		struct stmmac_rx_queue *rx_q = &priv->dma_conf.rx_queue[queue];
@@ -6510,10 +6567,20 @@ static int stmmac_rings_status_show(struct seq_file *seq, void *v)
 		seq_printf(seq, "RX Queue %d:\n", queue);
 
 		if (priv->extend_desc) {
+			if (!rx_q->dma_erx) {
+				seq_puts(seq, "Extended descriptor ring not allocated\n");
+				continue;
+			}
+
 			seq_printf(seq, "Extended descriptor ring:\n");
 			sysfs_display_ring((void *)rx_q->dma_erx,
 					   priv->dma_conf.dma_rx_size, 1, seq, rx_q->dma_rx_phy);
 		} else {
+			if (!rx_q->dma_rx) {
+				seq_puts(seq, "Descriptor ring not allocated\n");
+				continue;
+			}
+
 			seq_printf(seq, "Descriptor ring:\n");
 			sysfs_display_ring((void *)rx_q->dma_rx,
 					   priv->dma_conf.dma_rx_size, 0, seq, rx_q->dma_rx_phy);
@@ -6526,16 +6593,29 @@ static int stmmac_rings_status_show(struct seq_file *seq, void *v)
 		seq_printf(seq, "TX Queue %d:\n", queue);
 
 		if (priv->extend_desc) {
+			if (!tx_q->dma_etx) {
+				seq_puts(seq, "Extended descriptor ring not allocated\n");
+				continue;
+			}
+
 			seq_printf(seq, "Extended descriptor ring:\n");
 			sysfs_display_ring((void *)tx_q->dma_etx,
 					   priv->dma_conf.dma_tx_size, 1, seq, tx_q->dma_tx_phy);
 		} else if (!(tx_q->tbs & STMMAC_TBS_AVAIL)) {
+			if (!tx_q->dma_tx) {
+				seq_puts(seq, "Descriptor ring not allocated\n");
+				continue;
+			}
+
 			seq_printf(seq, "Descriptor ring:\n");
 			sysfs_display_ring((void *)tx_q->dma_tx,
 					   priv->dma_conf.dma_tx_size, 0, seq, tx_q->dma_tx_phy);
 		}
 	}
 
+out:
+	rtnl_unlock();
+
 	return 0;
 }
 DEFINE_SHOW_ATTRIBUTE(stmmac_rings_status);
-- 
2.34.1

Re: [PATCH net v5] net: stmmac: fix error path cleanup in DMA descriptor ring allocation

[netdev-bot+sinfo]

Hi!

This is an automated message. This series looks like a fix, but its
commit messages seem to be missing some information:

 - How the issue was discovered, e.g. hit in production, hit during
   development, syzbot report, manual code inspection, LLM or static
   analysis tool scan.

 - Whether the issue was actually triggered, or is only theoretical
   (e.g. found by code inspection). If it was triggered please include
   the symptoms, like the stack trace or error messages.

 - What hardware the change was tested on. For driver fixes please
   mention the device (and if relevant firmware version) used for
   testing, or say that the change was not tested on real hardware.

Please do not repost the series just to address the above. Instead,
reply to this email with the missing information, so that reviewers
can take it into account. If the series needs another revision for
other reasons, please include the information in the commit messages
then.

The evaluation is done by an LLM so it may be wrong, if you think
that is the case please reply and explain.

Re: [PATCH net v5] net: stmmac: fix error path cleanup in DMA descriptor ring allocation

[Maxime Chevallier]

Hi,

On 10/12/26 16:24, Ding Hui wrote:
> From: Ding Hui <dinghui@lixiang.com>
> 
> __alloc_dma_rx_desc_resources() and __alloc_dma_tx_desc_resources()
> allocate resources in multiple steps but return early on failure
> without cleaning up what they have already allocated. The outer
> error paths then call the free helpers on partially-initialized
> queues, which dereference pointers that were never allocated:
> 
>   - dma_free_rx_skbufs() and dma_free_rx_xskbufs() dereference
>     rx_q->buf_pool[i] via stmmac_free_rx_buffer(), but buf_pool
>     may be NULL if its kzalloc_objs() failed.
> 
>   - dma_free_tx_skbufs() dereferences tx_q->tx_skbuff_dma[i] via
>     stmmac_free_tx_buffer(), but tx_skbuff_dma may be NULL if its
>     kzalloc_objs() failed.
> 
>   - stmmac_free_tx_buffer() dereferences tx_q->xdpf[i] and
>     tx_q->tx_skbuff[i] (aliased through a union), but tx_skbuff
>     may be NULL if its allocation failed while tx_skbuff_dma
>     succeeded.
> 
> Fix this by making each allocation function responsible for undoing
> its own allocations on error, following the standard kernel error
> handling pattern of cleaning up in reverse order. Also add NULL
> checks in the free helpers as a defensive measure, since they may
> be called on partially-initialized queues.
> Additionally, make __free_dma_rx_desc_resources() and
> __free_dma_tx_desc_resources() clear the pointers they free, so that
> the NULL guards in the free helpers hold reliably when the long-lived
> priv->dma_conf is reused across XDP open/release cycles.
> Free the RX resources in alloc_dma_desc_resources() when the TX
> allocation fails, as the callers only free dma_conf itself on
> that path.
> After __stmmac_open() copies a temporary dma_conf into priv->dma_conf,
> release the descriptor resources through priv->dma_conf on an open
> failure. This keeps the long-lived configuration consistent with the
> resource cleanup while callers only free the temporary container.
> Finally, hold RTNL while descriptors_status inspects the descriptor
> rings. This serializes the debugfs reader with control-plane resource
> teardown paths and allows it to safely report queues whose descriptor
> rings are not allocated. Skip queues whose descriptor rings are not
> allocated in stmmac_rings_status_show() to avoid dereferencing a NULL
> pointer.
> 
> Signed-off-by: Ding Hui <dinghui@lixiang.com>

In V1 Andrew requested that this targets net-next yet this series kept
targetting the "net" tree since then.

I think this is an omission on your side as you replied to the bots that
you removed the Fixes: tag on purpose :) You need to have "net-next" in
the patch topic : [PATCH net-next v5]

This is starting to look good, but as you need to respin, is it possible
that you split that patch down into simpler patches ? There are multiple
classes of problems being addressed here :
 - Error paths being reworked
 - Null checks being added
 - Some pointers being Nulled

It would make it easier to digest during review.

Thanks,

Maxime

> 
> ---
> Changes in v5:
>   - Release copied descriptor resources through priv->dma_conf when
>     __stmmac_open() fails, avoiding stale pointers in the long-lived
>     configuration.
>   - Hold RTNL while descriptors_status reads descriptor rings.
>   - Correct the commit message to refer to descriptors_status as a
>     debugfs entry rather than a sysfs entry.
>   - Link to v4:
>     https://lore.kernel.org/netdev/20261001035045.3305816-1-dinghui1111@163.com/
> Changes in v4:
>   - Free the RX resources in alloc_dma_desc_resources() when the TX
>     allocation fails.
>   - Skip queues whose descriptor rings are not allocated in
>     stmmac_rings_status_show() and print a hint instead.
>   - Link to v3:
>     https://lore.kernel.org/netdev/20260919121436.1642724-1-dinghui1111@163.com/
> Changes in v3:
>   - Use addr directly in __alloc_dma_rx_desc_resources() error path
>     instead of the if/else block on rx_q->dma_erx/dma_rx.
>   - Clear the freed pointers in __free_dma_rx_desc_resources() and
>     __free_dma_tx_desc_resources().
>   - Link to v2:
>     https://lore.kernel.org/netdev/20260905154654.1725313-1-dinghui1111@163.com/
> Changes in v2:
>   - Instead of only adding NULL checks in the free helpers, also fix
>     __alloc_dma_rx_desc_resources() and __alloc_dma_tx_desc_resources()
>     to clean up their own allocations on error, as suggested by Andrew.
>   - Update commit message.
>   - Link to v1:
>     https://lore.kernel.org/netdev/20260830040610.1156008-1-dinghui1111@163.com/
> ---
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 112 +++++++++++++++---
>  1 file changed, 96 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index f2fc89176654..852a8b103c45 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1728,7 +1728,7 @@ static void stmmac_free_tx_buffer(struct stmmac_priv *priv,
>  					 DMA_TO_DEVICE);
>  	}
>  
> -	if (tx_q->xdpf[i] &&
> +	if (tx_q->xdpf && tx_q->xdpf[i] &&
>  	    (tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_XDP_TX ||
>  	     tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_XDP_NDO)) {
>  		xdp_return_frame(tx_q->xdpf[i]);
> @@ -1738,7 +1738,7 @@ static void stmmac_free_tx_buffer(struct stmmac_priv *priv,
>  	if (tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_XSK_TX)
>  		tx_q->xsk_frames_done++;
>  
> -	if (tx_q->tx_skbuff[i] &&
> +	if (tx_q->tx_skbuff && tx_q->tx_skbuff[i] &&
>  	    tx_q->tx_skbuff_dma[i].buf_type == STMMAC_TXBUF_T_SKB) {
>  		dev_kfree_skb_any(tx_q->tx_skbuff[i]);
>  		tx_q->tx_skbuff[i] = NULL;
> @@ -1761,6 +1761,10 @@ static void dma_free_rx_skbufs(struct stmmac_priv *priv,
>  	struct stmmac_rx_queue *rx_q = &dma_conf->rx_queue[queue];
>  	int i;
>  
> +	/* buf_pool may not be allocated if alloc failed early */
> +	if (!rx_q->buf_pool)
> +		return;
> +
>  	for (i = 0; i < dma_conf->dma_rx_size; i++)
>  		stmmac_free_rx_buffer(priv, rx_q, i);
>  }
> @@ -1802,6 +1806,10 @@ static void dma_free_rx_xskbufs(struct stmmac_priv *priv,
>  	struct stmmac_rx_queue *rx_q = &dma_conf->rx_queue[queue];
>  	int i;
>  
> +	/* buf_pool may not be allocated if alloc failed early */
> +	if (!rx_q->buf_pool)
> +		return;
> +
>  	for (i = 0; i < dma_conf->dma_rx_size; i++) {
>  		struct stmmac_rx_buffer *buf = &rx_q->buf_pool[i];
>  
> @@ -2097,6 +2105,10 @@ static void dma_free_tx_skbufs(struct stmmac_priv *priv,
>  	struct stmmac_tx_queue *tx_q = &dma_conf->tx_queue[queue];
>  	int i;
>  
> +	/* tx_skbuff_dma may not be allocated if alloc failed early */
> +	if (!tx_q->tx_skbuff_dma)
> +		return;
> +
>  	tx_q->xsk_frames_done = 0;
>  
>  	for (i = 0; i < dma_conf->dma_tx_size; i++)
> @@ -2154,13 +2166,20 @@ static void __free_dma_rx_desc_resources(struct stmmac_priv *priv,
>  	size = stmmac_get_rx_desc_size(priv) * dma_conf->dma_rx_size;
>  
>  	dma_free_coherent(priv->device, size, addr, rx_q->dma_rx_phy);
> +	rx_q->dma_erx = NULL;
> +	rx_q->dma_rx = NULL;
> +	rx_q->dma_rx_phy = 0;
>  
>  	if (xdp_rxq_info_is_reg(&rx_q->xdp_rxq))
>  		xdp_rxq_info_unreg(&rx_q->xdp_rxq);
>  
>  	kfree(rx_q->buf_pool);
> -	if (rx_q->page_pool)
> +	rx_q->buf_pool = NULL;
> +
> +	if (rx_q->page_pool) {
>  		page_pool_destroy(rx_q->page_pool);
> +		rx_q->page_pool = NULL;
> +	}
>  }
>  
>  static void free_dma_rx_desc_resources(struct stmmac_priv *priv,
> @@ -2202,9 +2221,16 @@ static void __free_dma_tx_desc_resources(struct stmmac_priv *priv,
>  	size = stmmac_get_tx_desc_size(priv, tx_q) * dma_conf->dma_tx_size;
>  
>  	dma_free_coherent(priv->device, size, addr, tx_q->dma_tx_phy);
> +	tx_q->dma_etx = NULL;
> +	tx_q->dma_entx = NULL;
> +	tx_q->dma_tx = NULL;
> +	tx_q->dma_tx_phy = 0;
>  
>  	kfree(tx_q->tx_skbuff_dma);
> +	tx_q->tx_skbuff_dma = NULL;
> +
>  	kfree(tx_q->tx_skbuff);
> +	tx_q->tx_skbuff = NULL;
>  }
>  
>  static void free_dma_tx_desc_resources(struct stmmac_priv *priv,
> @@ -2272,15 +2298,19 @@ static int __alloc_dma_rx_desc_resources(struct stmmac_priv *priv,
>  	}
>  
>  	rx_q->buf_pool = kzalloc_objs(*rx_q->buf_pool, dma_conf->dma_rx_size);
> -	if (!rx_q->buf_pool)
> -		return -ENOMEM;
> +	if (!rx_q->buf_pool) {
> +		ret = -ENOMEM;
> +		goto err_destroy_pool;
> +	}
>  
>  	size = stmmac_get_rx_desc_size(priv) * dma_conf->dma_rx_size;
>  
>  	addr = dma_alloc_coherent(priv->device, size, &rx_q->dma_rx_phy,
>  				  GFP_KERNEL);
> -	if (!addr)
> -		return -ENOMEM;
> +	if (!addr) {
> +		ret = -ENOMEM;
> +		goto err_free_buf_pool;
> +	}
>  
>  	if (priv->extend_desc)
>  		rx_q->dma_erx = addr;
> @@ -2296,10 +2326,22 @@ static int __alloc_dma_rx_desc_resources(struct stmmac_priv *priv,
>  	ret = xdp_rxq_info_reg(&rx_q->xdp_rxq, priv->dev, queue, napi_id);
>  	if (ret) {
>  		netdev_err(priv->dev, "Failed to register xdp rxq info\n");
> -		return -EINVAL;
> +		goto err_free_dma;
>  	}
>  
>  	return 0;
> +
> +err_free_dma:
> +	dma_free_coherent(priv->device, size, addr, rx_q->dma_rx_phy);
> +	rx_q->dma_erx = NULL;
> +	rx_q->dma_rx = NULL;
> +err_free_buf_pool:
> +	kfree(rx_q->buf_pool);
> +	rx_q->buf_pool = NULL;
> +err_destroy_pool:
> +	page_pool_destroy(rx_q->page_pool);
> +	rx_q->page_pool = NULL;
> +	return ret;
>  }
>  
>  static int alloc_dma_rx_desc_resources(struct stmmac_priv *priv,
> @@ -2352,14 +2394,14 @@ static int __alloc_dma_tx_desc_resources(struct stmmac_priv *priv,
>  
>  	tx_q->tx_skbuff = kzalloc_objs(struct sk_buff *, dma_conf->dma_tx_size);
>  	if (!tx_q->tx_skbuff)
> -		return -ENOMEM;
> +		goto err_free_skbuff_dma;
>  
>  	size = stmmac_get_tx_desc_size(priv, tx_q) * dma_conf->dma_tx_size;
>  
>  	addr = dma_alloc_coherent(priv->device, size,
>  				  &tx_q->dma_tx_phy, GFP_KERNEL);
>  	if (!addr)
> -		return -ENOMEM;
> +		goto err_free_skbuff;
>  
>  	if (priv->extend_desc)
>  		tx_q->dma_etx = addr;
> @@ -2369,6 +2411,14 @@ static int __alloc_dma_tx_desc_resources(struct stmmac_priv *priv,
>  		tx_q->dma_tx = addr;
>  
>  	return 0;
> +
> +err_free_skbuff:
> +	kfree(tx_q->tx_skbuff);
> +	tx_q->tx_skbuff = NULL;
> +err_free_skbuff_dma:
> +	kfree(tx_q->tx_skbuff_dma);
> +	tx_q->tx_skbuff_dma = NULL;
> +	return -ENOMEM;
>  }
>  
>  static int alloc_dma_tx_desc_resources(struct stmmac_priv *priv,
> @@ -2411,6 +2461,8 @@ static int alloc_dma_desc_resources(struct stmmac_priv *priv,
>  		return ret;
>  
>  	ret = alloc_dma_tx_desc_resources(priv, dma_conf);
> +	if (ret)
> +		free_dma_rx_desc_resources(priv, dma_conf);
>  
>  	return ret;
>  }
> @@ -4182,6 +4234,7 @@ static int __stmmac_open(struct net_device *dev,
>  
>  	stmmac_release_ptp(priv);
>  init_error:
> +	free_dma_desc_resources(priv, &priv->dma_conf);
>  	return ret;
>  }
>  
> @@ -4214,8 +4267,13 @@ static int stmmac_open(struct net_device *dev)
>  	}
>  
>  	ret = __stmmac_open(dev, dma_conf);
> -	if (ret)
> -		goto err_serdes;
> +	if (ret) {
> +		stmmac_legacy_serdes_power_down(priv);
> +		phylink_disconnect_phy(priv->phylink);
> +		pm_runtime_put(priv->device);
> +		kfree(dma_conf);
> +		return ret;
> +	}
>  
>  	kfree(dma_conf);
>  
> @@ -4224,8 +4282,6 @@ static int stmmac_open(struct net_device *dev)
>  
>  	return ret;
>  
> -err_serdes:
> -	stmmac_legacy_serdes_power_down(priv);
>  err_disconnect_phy:
>  	phylink_disconnect_phy(priv->phylink);
>  err_runtime_pm:
> @@ -6130,7 +6186,6 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
>  
>  		ret = __stmmac_open(dev, dma_conf);
>  		if (ret) {
> -			free_dma_desc_resources(priv, dma_conf);
>  			kfree(dma_conf);
>  			netdev_err(priv->dev, "failed reopening the interface after MTU change\n");
>  			return ret;
> @@ -6501,8 +6556,10 @@ static int stmmac_rings_status_show(struct seq_file *seq, void *v)
>  	u8 tx_count = priv->plat->tx_queues_to_use;
>  	u8 queue;
>  
> +	rtnl_lock();
> +
>  	if ((dev->flags & IFF_UP) == 0)
> -		return 0;
> +		goto out;
>  
>  	for (queue = 0; queue < rx_count; queue++) {
>  		struct stmmac_rx_queue *rx_q = &priv->dma_conf.rx_queue[queue];
> @@ -6510,10 +6567,20 @@ static int stmmac_rings_status_show(struct seq_file *seq, void *v)
>  		seq_printf(seq, "RX Queue %d:\n", queue);
>  
>  		if (priv->extend_desc) {
> +			if (!rx_q->dma_erx) {
> +				seq_puts(seq, "Extended descriptor ring not allocated\n");
> +				continue;
> +			}
> +
>  			seq_printf(seq, "Extended descriptor ring:\n");
>  			sysfs_display_ring((void *)rx_q->dma_erx,
>  					   priv->dma_conf.dma_rx_size, 1, seq, rx_q->dma_rx_phy);
>  		} else {
> +			if (!rx_q->dma_rx) {
> +				seq_puts(seq, "Descriptor ring not allocated\n");
> +				continue;
> +			}
> +
>  			seq_printf(seq, "Descriptor ring:\n");
>  			sysfs_display_ring((void *)rx_q->dma_rx,
>  					   priv->dma_conf.dma_rx_size, 0, seq, rx_q->dma_rx_phy);
> @@ -6526,16 +6593,29 @@ static int stmmac_rings_status_show(struct seq_file *seq, void *v)
>  		seq_printf(seq, "TX Queue %d:\n", queue);
>  
>  		if (priv->extend_desc) {
> +			if (!tx_q->dma_etx) {
> +				seq_puts(seq, "Extended descriptor ring not allocated\n");
> +				continue;
> +			}
> +
>  			seq_printf(seq, "Extended descriptor ring:\n");
>  			sysfs_display_ring((void *)tx_q->dma_etx,
>  					   priv->dma_conf.dma_tx_size, 1, seq, tx_q->dma_tx_phy);
>  		} else if (!(tx_q->tbs & STMMAC_TBS_AVAIL)) {
> +			if (!tx_q->dma_tx) {
> +				seq_puts(seq, "Descriptor ring not allocated\n");
> +				continue;
> +			}
> +
>  			seq_printf(seq, "Descriptor ring:\n");
>  			sysfs_display_ring((void *)tx_q->dma_tx,
>  					   priv->dma_conf.dma_tx_size, 0, seq, tx_q->dma_tx_phy);
>  		}
>  	}
>  
> +out:
> +	rtnl_unlock();
> +
>  	return 0;
>  }
>  DEFINE_SHOW_ATTRIBUTE(stmmac_rings_status);

Re:Re: [PATCH net v5] net: stmmac: fix error path cleanup in DMA descriptor ring allocation

[Ding Hui]

Hi,
Thanks for the review.

At 2026-10-16 22:44:35, "Maxime Chevallier" <maxime.chevallier@bootlin.com> wrote:
>Hi,
>
>On 10/12/26 16:24, Ding Hui wrote:
>> From: Ding Hui <dinghui@lixiang.com>
>> 
>> __alloc_dma_rx_desc_resources() and __alloc_dma_tx_desc_resources()
>> allocate resources in multiple steps but return early on failure
>> without cleaning up what they have already allocated. The outer
>> error paths then call the free helpers on partially-initialized
>> queues, which dereference pointers that were never allocated:
>> 
>>   - dma_free_rx_skbufs() and dma_free_rx_xskbufs() dereference
>>     rx_q->buf_pool[i] via stmmac_free_rx_buffer(), but buf_pool
>>     may be NULL if its kzalloc_objs() failed.
>> 
>>   - dma_free_tx_skbufs() dereferences tx_q->tx_skbuff_dma[i] via
>>     stmmac_free_tx_buffer(), but tx_skbuff_dma may be NULL if its
>>     kzalloc_objs() failed.
>> 
>>   - stmmac_free_tx_buffer() dereferences tx_q->xdpf[i] and
>>     tx_q->tx_skbuff[i] (aliased through a union), but tx_skbuff
>>     may be NULL if its allocation failed while tx_skbuff_dma
>>     succeeded.
>> 
>> Fix this by making each allocation function responsible for undoing
>> its own allocations on error, following the standard kernel error
>> handling pattern of cleaning up in reverse order. Also add NULL
>> checks in the free helpers as a defensive measure, since they may
>> be called on partially-initialized queues.
>> Additionally, make __free_dma_rx_desc_resources() and
>> __free_dma_tx_desc_resources() clear the pointers they free, so that
>> the NULL guards in the free helpers hold reliably when the long-lived
>> priv->dma_conf is reused across XDP open/release cycles.
>> Free the RX resources in alloc_dma_desc_resources() when the TX
>> allocation fails, as the callers only free dma_conf itself on
>> that path.
>> After __stmmac_open() copies a temporary dma_conf into priv->dma_conf,
>> release the descriptor resources through priv->dma_conf on an open
>> failure. This keeps the long-lived configuration consistent with the
>> resource cleanup while callers only free the temporary container.
>> Finally, hold RTNL while descriptors_status inspects the descriptor
>> rings. This serializes the debugfs reader with control-plane resource
>> teardown paths and allows it to safely report queues whose descriptor
>> rings are not allocated. Skip queues whose descriptor rings are not
>> allocated in stmmac_rings_status_show() to avoid dereferencing a NULL
>> pointer.
>> 
>> Signed-off-by: Ding Hui <dinghui@lixiang.com>
>
>In V1 Andrew requested that this targets net-next yet this series kept
>targetting the "net" tree since then.
>
>I think this is an omission on your side as you replied to the bots that
>you removed the Fixes: tag on purpose :) You need to have "net-next" in
>the patch topic : [PATCH net-next v5]
>
The "net" prefix is indeed an omission on my side. Andrew asked for
net-next targeting back in v1, and I kept the wrong subject prefix
when respinning. The next revision will be sent as [PATCH net-next v6].

>This is starting to look good, but as you need to respin, is it possible
>that you split that patch down into simpler patches ? There are multiple
>classes of problems being addressed here :
> - Error paths being reworked
> - Null checks being added
> - Some pointers being Nulled
>
>It would make it easier to digest during review.
>
Agreed. Here is the plan — 4 patches, ordered as follows:

  1/4: add NULL guards in the free helpers and clear the pointers
       they free, so that a NULL pointer reliably means "not
       allocated";

  2/4: rework the allocation error paths, making
       __alloc_dma_rx_desc_resources() and
       __alloc_dma_tx_desc_resources() undo their own allocations on
       error, and free the RX resources when the TX allocation
       fails;

  3/4: release the descriptor resources through priv->dma_conf when
       __stmmac_open() fails after copying the temporary dma_conf,
       adjusting the callers accordingly;

  4/4: hold RTNL while the descriptors_status debugfs entry inspects
       the rings, and skip queues whose rings are not allocated.

Does this split and ordering look reasonable? If so, I'll
send v6 shortly.

Best regards,
Ding Hui