[PATCH net v2] net: stmmac: Fix accessing freed irq affinity_hint

[PATCH net v2] net: stmmac: Fix accessing freed irq affinity_hint

[Qingfang Deng]

The cpumask should not be a local variable, since its pointer is saved
to irq_desc and may be accessed from procfs.
To fix it, use the persistent mask cpumask_of(cpu#).

Cc: stable@vger.kernel.org
Fixes: 8deec94c6040 ("net: stmmac: set IRQ affinity hint for multi MSI vectors")
Signed-off-by: Qingfang Deng <dqfext@gmail.com>
---
v2: use cpumask_of()

 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b22417167cac..ec63452187d0 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3667,7 +3667,6 @@ static int stmmac_request_irq_multi_msi(struct net_device *dev)
 {
 	struct stmmac_priv *priv = netdev_priv(dev);
 	enum request_irq_err irq_err;
-	cpumask_t cpu_mask;
 	int irq_idx = 0;
 	char *int_name;
 	int ret;
@@ -3796,9 +3795,8 @@ static int stmmac_request_irq_multi_msi(struct net_device *dev)
 			irq_idx = i;
 			goto irq_error;
 		}
-		cpumask_clear(&cpu_mask);
-		cpumask_set_cpu(i % num_online_cpus(), &cpu_mask);
-		irq_set_affinity_hint(priv->rx_irq[i], &cpu_mask);
+		irq_set_affinity_hint(priv->rx_irq[i],
+				      cpumask_of(i % num_online_cpus()));
 	}
 
 	/* Request Tx MSI irq */
@@ -3821,9 +3819,8 @@ static int stmmac_request_irq_multi_msi(struct net_device *dev)
 			irq_idx = i;
 			goto irq_error;
 		}
-		cpumask_clear(&cpu_mask);
-		cpumask_set_cpu(i % num_online_cpus(), &cpu_mask);
-		irq_set_affinity_hint(priv->tx_irq[i], &cpu_mask);
+		irq_set_affinity_hint(priv->tx_irq[i],
+				      cpumask_of(i % num_online_cpus()));
 	}
 
 	return 0;
-- 
2.43.0

RE: [PATCH net v2] net: stmmac: Fix accessing freed irq affinity_hint

[Keller, Jacob E]

> -----Original Message-----
> From: Qingfang Deng <dqfext@gmail.com>
> Sent: Monday, March 17, 2025 8:24 PM
> To: Andrew Lunn <andrew+netdev@lunn.ch>; David S. Miller
> <davem@davemloft.net>; Dumazet, Eric <edumazet@google.com>; Jakub Kicinski
> <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; Maxime Coquelin
> <mcoquelin.stm32@gmail.com>; Alexandre Torgue
> <alexandre.torgue@foss.st.com>; Ong, Boon Leong
> <boon.leong.ong@intel.com>; netdev@vger.kernel.org; linux-stm32@st-md-
> mailman.stormreply.com; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org
> Cc: stable@vger.kernel.org
> Subject: [PATCH net v2] net: stmmac: Fix accessing freed irq affinity_hint
> 
> The cpumask should not be a local variable, since its pointer is saved
> to irq_desc and may be accessed from procfs.
> To fix it, use the persistent mask cpumask_of(cpu#).
> 
> Cc: stable@vger.kernel.org
> Fixes: 8deec94c6040 ("net: stmmac: set IRQ affinity hint for multi MSI vectors")
> Signed-off-by: Qingfang Deng <dqfext@gmail.com>
> ---
> v2: use cpumask_of()
> 

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

Re: [PATCH net v2] net: stmmac: Fix accessing freed irq affinity_hint

[Jakub Kicinski]

On Tue, 18 Mar 2025 11:24:23 +0800 Qingfang Deng wrote:
> -		cpumask_clear(&cpu_mask);
> -		cpumask_set_cpu(i % num_online_cpus(), &cpu_mask);
> -		irq_set_affinity_hint(priv->rx_irq[i], &cpu_mask);
> +		irq_set_affinity_hint(priv->rx_irq[i],
> +				      cpumask_of(i % num_online_cpus()));

This does fix the bug you're targeting, but FWIW num_online_cpus() 
is not great in general. The online CPU mask can be sparse.
You may want to look into finding 'nth' online CPU instead of the naive
modulo as a follow up.

Re: [PATCH net v2] net: stmmac: Fix accessing freed irq affinity_hint

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 18 Mar 2025 11:24:23 +0800 you wrote:
> The cpumask should not be a local variable, since its pointer is saved
> to irq_desc and may be accessed from procfs.
> To fix it, use the persistent mask cpumask_of(cpu#).
> 
> Cc: stable@vger.kernel.org
> Fixes: 8deec94c6040 ("net: stmmac: set IRQ affinity hint for multi MSI vectors")
> Signed-off-by: Qingfang Deng <dqfext@gmail.com>
> 
> [...]

Here is the summary with links:
  - [net,v2] net: stmmac: Fix accessing freed irq affinity_hint
    https://git.kernel.org/netdev/net/c/c60d101a226f

You are awesome, thank you!
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