[PATCH net-next v6 0/4] net: stmmac: fix DMA descriptor ring cleanup issues

[Ding Hui <dinghui1111@163.com>]

From: Ding Hui <dinghui@lixiang.com>

Hello,

This series fixes the NULL pointer dereferences in the stmmac TX/RX
DMA resource cleanup paths and the associated error path issues,
found on a DWMAC platform whose descriptor ring allocation may fail
under memory pressure.

Patch 1 adds NULL guards in the free helpers and makes them clear
the pointers they free, so that a NULL pointer reliably means "not
allocated" for the long-lived priv->dma_conf.

Patch 2 makes the per-queue allocation functions undo their own
allocations on error, instead of leaving the cleanup to the outer
error paths that would then walk partially-initialized queues.

Patch 3 releases the descriptor resources through priv->dma_conf
when __stmmac_open() fails after copying the temporary dma_conf, so
the long-lived configuration stays consistent with the resource
cleanup.

Patch 4 holds RTNL around the descriptors_status debugfs reader and
skips queues whose rings are not allocated.

This series is rebased on top of the current net-next.

Changes in v6:
  - Split the single patch into a four-patch series as requested
    during review: NULL guards and pointer clearing, allocation
    error paths, descriptor resource release through priv->dma_conf
    on open failure, and the descriptors_status debugfs locking.
  - Merge the descriptor resource release with the ptp_error unwind
    from 8181678a92f0 and rebase on top of the current net-next.
  - Use the "net-next" subject prefix, which was requested back in
    v1 but mistakenly kept as "net" in all previous revisions.
  - Link to v5:
    https://lore.kernel.org/netdev/20261012142458.2845385-1-dinghui1111@163.com/

Changes in v5:
  - Release the descriptor resources through priv->dma_conf when
    __stmmac_open() fails, avoiding stale pointers in the
    long-lived configuration.
  - Hold RTNL while descriptors_status reads the descriptor rings.
  - 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.
  - Link to v1:
    https://lore.kernel.org/netdev/20260830040610.1156008-1-dinghui1111@163.com/

Ding Hui (4):
  net: stmmac: guard against NULL pointers when freeing TX/RX buffers
  net: stmmac: clean up partially allocated DMA rings on error
  net: stmmac: release descriptor resources through priv->dma_conf on
    open failure
  net: stmmac: hold RTNL when reading descriptor rings in
    descriptors_status

 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 115 +++++++++++++++---
 1 file changed, 98 insertions(+), 17 deletions(-)

--
2.34.1