[PATCH AUTOSEL 6.17-5.10] net: stmmac: Check stmmac_hw_setup() in stmmac_resume()

[Sasha Levin <sashal@kernel.org>]

From: Tiezhu Yang <yangtiezhu@loongson.cn>

[ Upstream commit 6896c2449a1858acb643014894d01b3a1223d4e5 ]

stmmac_hw_setup() may return 0 on success and an appropriate negative
integer as defined in errno.h file on failure, just check it and then
return early if failed in stmmac_resume().

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://patch.msgid.link/20250811073506.27513-2-yangtiezhu@loongson.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

YES

- What it fixes
  - The resume path ignores the return value of stmmac_hw_setup(), which
    is documented to return 0 on success or -errno on failure. See the
    function signature and comment in
    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:3396. Inside that
    function, critical steps like stmmac_init_dma_engine() can fail and
    return -errno (e.g., invalid DMA configuration, failed reset), see
    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:3410.
  - In the current resume path, the return from stmmac_hw_setup() is not
    checked: drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:8033. The
    code then proceeds to run initialization and enablement sequences
    (e.g., stmmac_init_coalesce(), stmmac_set_rx_mode(),
    stmmac_enable_all_queues(), stmmac_enable_all_dma_irq()), which
    operate on hardware that may not be properly initialized after a
    failure, risking hangs or crashes. These calls are at
    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:8034,
    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:8035,
    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:8039, and
    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:8040,
    respectively.
  - The open path already does the right thing by checking the return
    value and bailing on failure with an error message
    (drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:3977). The resume
    path should be consistent with this.

- What the patch changes
  - It assigns the return value of stmmac_hw_setup() to ret and checks
    for errors. On error it logs and returns early after correctly
    releasing the held locks (mutex_unlock and rtnl_unlock). This
    prevents further use of uninitialized DMA/MAC state and keeps error
    handling consistent with the open path.

- Scope and risk
  - Minimal and contained: only the stmmac driver, no API/ABI changes,
    no feature additions. The change is a straightforward error-path fix
    and mirrors existing patterns in __stmmac_open().
  - Locking is handled correctly: the new early-return path explicitly
    releases both the private mutex and rtnl lock before returning,
    avoiding deadlocks.
  - User impact: prevents resume-time failures from cascading into
    deeper faults by stopping early and reporting a clear error.

- Context and applicability
  - Many stmmac glue drivers call stmmac_resume() directly, so this
    affects a broad set of platforms (e.g.,
    drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c:1183,
    drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c:2066).
  - The fix does not depend on newer phylink changes (e.g.,
    phylink_prepare_resume()). While newer mainline code refines phylink
    sequencing, this error check is orthogonal and safe to apply to
    stable branches that don’t have those changes.
  - The stmmac_resume() in current stable series has the same
    problematic pattern (call stmmac_hw_setup() without checking its
    return), so the patch is directly relevant.

- Stable rules assessment
  - Fixes a real bug that can lead to faults after resume.
  - Small, localized change with minimal regression risk.
  - No architectural or user-visible feature changes.
  - Affects only the stmmac driver; well-scoped for backporting.

Conclusion: This is a clear, low-risk bug fix that prevents unsafe
continuation after hardware initialization failures during resume. It
should be backported to stable kernels.

 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 7b16d1207b80c..b9f55e4e360fb 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -7977,7 +7977,14 @@ int stmmac_resume(struct device *dev)
 	stmmac_free_tx_skbufs(priv);
 	stmmac_clear_descriptors(priv, &priv->dma_conf);
 
-	stmmac_hw_setup(ndev, false);
+	ret = stmmac_hw_setup(ndev, false);
+	if (ret < 0) {
+		netdev_err(priv->dev, "%s: Hw setup failed\n", __func__);
+		mutex_unlock(&priv->lock);
+		rtnl_unlock();
+		return ret;
+	}
+
 	stmmac_init_coalesce(priv);
 	phylink_rx_clk_stop_block(priv->phylink);
 	stmmac_set_rx_mode(ndev);
-- 
2.51.0