From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Vladimir Oltean <vladimir.oltean@nxp.com>,
	Florian Fainelli <florian.fainelli@broadcom.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12 1193/1376] net: dsa: b53: fix error propagation from b53_fdb_dump()
Date: Sat, 12 Sep 2026 09:00:19 +0200
Message-ID: <20260912065634.139177659@linuxfoundation.org>
In-Reply-To: <20260912065607.535295758@linuxfoundation.org>
References: <20260912065607.535295758@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vladimir Oltean <vladimir.oltean@nxp.com>

[ Upstream commit 4f1d06cf8aaa9d2cb18e5ee8835aff6177256bc6 ]

The blamed commit replaced "return ret" statements in b53_fdb_dump()
with "break;" which jumps to the mutex_unlock() -> return 0 section.

This is notably problematic because it swallows errors from the
b53_fdb_copy() -> cb() path, and this will result in FDB dump truncation
when the netlink skb overflows - see commit 21b52fed928e ("net: dsa:
sja1105: fix broken backpressure in .port_fdb_dump").

Let's go back to "return ret". We don't need to preinitialize "ret" with
0, because the "do {} while" block guarantees we cannot reach the end of
the function without at least once calling b53_arl_search_wait(), which
will have initialized ret to some valid value.

Fixes: f7eb4a1c0864 ("net: dsa: b53: serialize access to the ARL table")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20260812201121.2012356-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/dsa/b53/b53_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
index 0b666a77ea977..04027cbefddba 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -2020,7 +2020,7 @@ int b53_fdb_dump(struct dsa_switch *ds, int port,
 
 	mutex_unlock(&priv->arl_mutex);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL(b53_fdb_dump);
 
-- 
2.53.0