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Message-ID: <aLVzvAJCjwpWPMU8@shredder>
Date: Mon, 1 Sep 2025 13:21:48 +0300
From: Ido Schimmel <idosch@...dia.com>
To: Petr Machata <petrm@...dia.com>
Cc: Miaoqian Lin <linmq006@...il.com>, Andrew Lunn <andrew+netdev@...n.ch>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Vadim Pasternak <vadimp@...dia.com>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mlxsw: core_env: Fix stack info leak in
mlxsw_env_linecard_modules_power_mode_apply
On Mon, Sep 01, 2025 at 11:10:19AM +0200, Petr Machata wrote:
>
> Ido Schimmel <idosch@...dia.com> writes:
>
> > On Sat, Aug 30, 2025 at 04:11:22PM +0800, Miaoqian Lin wrote:
> >> The extack was declared on the stack without initialization.
> >> If mlxsw_env_set_module_power_mode_apply() fails to set extack,
> >> accessing extack._msg could leak information.
> >
> > Unless I'm missing something, I don't see a case where
> > mlxsw_env_set_module_power_mode_apply() returns an error without setting
> > extack. IOW, I don't see how this info leak can happen with existing
> > code.
>
> Yeah, I agree it all looks initialized.
>
> The patch still makes sense to me, it will make the code less prone to
> footguns in the future. The expectation with extack is that it's
> optional, though functions that take the argument typically also take
> care to set it (or propagate further). But here it is mandatory to
> initialize it, or else things break. With the patch we'd get a
> "(null)\n" instead of garbage. Not great, but better.
Can be solved with this diff:
diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_env.c b/drivers/net/ethernet/mellanox/mlxsw/core_env.c
index 294e758f1067..8908520f39d9 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core_env.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core_env.c
@@ -1332,7 +1332,7 @@ mlxsw_env_linecard_modules_power_mode_apply(struct mlxsw_core *mlxsw_core,
for (i = 0; i < env->line_cards[slot_index]->module_count; i++) {
enum ethtool_module_power_mode_policy policy;
struct mlxsw_env_module_info *module_info;
- struct netlink_ext_ack extack;
+ struct netlink_ext_ack extack = {};
int err;
module_info = &env->line_cards[slot_index]->module_info[i];
@@ -1340,7 +1340,7 @@ mlxsw_env_linecard_modules_power_mode_apply(struct mlxsw_core *mlxsw_core,
err = mlxsw_env_set_module_power_mode_apply(mlxsw_core,
slot_index, i,
policy, &extack);
- if (err)
+ if (err && extack._msg)
dev_err(env->bus_info->dev, "%s\n", extack._msg);
}
}
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