[PATCH net] net: dsa: b53: fix error propagation from b53_fdb_dump()

[PATCH net] net: dsa: b53: fix error propagation from b53_fdb_dump()

[Vladimir Oltean]

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>
---
Compile-tested only. Noticed while reviewing other things.

 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 ba1266cd70c3..c4c8513ae486 100644
--- a/drivers/net/dsa/b53/b53_common.c
+++ b/drivers/net/dsa/b53/b53_common.c
@@ -2274,7 +2274,7 @@ int b53_fdb_dump(struct dsa_switch *ds, int port,
 
 	mutex_unlock(&priv->arl_mutex);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL(b53_fdb_dump);
 
-- 
2.43.0

Re: [PATCH net] net: dsa: b53: fix error propagation from b53_fdb_dump()

[Florian Fainelli]

On 8/12/26 13:11, Vladimir Oltean wrote:
> 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>
-- 
Florian