Subject: Re: [PATCH iwl-net v1] igc: fix potential skb leak in igc_fpe_xmit_smd_frame()

From: Simon Horman <[email-masked]>
Date: Fri, 3 Apr 2026 15:05:55 +0100

On Sun, Mar 29, 2026 at 02:50:49PM +0000, Kohei Enju wrote:
> When igc_fpe_init_tx_descriptor() fails, no one takes care of an
> allocated skb, leaking it. [1]
> 
> Use dev_kfree_skb_any() on failure.
> Also call igc_flush_tx_descriptors() only on success.
> 
> [1]
> unreferenced object 0xffff88813aee1b40 (size 224):
>   comm "softirq", pid 0, jiffies 4294709256
> [...]
>   backtrace (crc dee31384):
>     kmem_cache_alloc_node_noprof+0x54f/0x640
>     __alloc_skb+0xd9/0x5b0
>     igc_fpe_xmit_smd_frame.isra.0+0xad/0x510
>     igc_fpe_send_mpacket+0x32/0x80
> [...]
> 
> Fixes: 5422570c0010 ("igc: add support for frame preemption verification")
> Signed-off-by: Kohei Enju <[email-masked]>

I am wondering if we can achieve this while sticking to the idiom
that the main thread of execution is for the non-error flow,
while conditions handle errors.

Something like this (completely untested!):

diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index 8a110145bfee..02dd9f0290a3 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -109,10 +109,16 @@ static int igc_fpe_xmit_smd_frame(struct igc_adapter *adapter,
 	__netif_tx_lock(nq, cpu);
 
 	err = igc_fpe_init_tx_descriptor(ring, skb, type);
-	igc_flush_tx_descriptors(ring);
+	if (err)
+		goto err_free_skb_any;
 
+	igc_flush_tx_descriptors(ring);
 	__netif_tx_unlock(nq);
+	return 0;
 
+err_free_skb_any:
+	__netif_tx_unlock(nq);
+	dev_kfree_skb_any(skb);
 	return err;
 }