[lvc-project] [PATCH 5.10 004/317] r8169: Fix possible ring buffer corruption on fragmented Tx packets.

[Ken Milmore]

On 13/06/2024 18:21, Alexey Khoroshilov wrote:
> On 13.06.2024 14:30, Greg Kroah-Hartman wrote:
>> 5.10-stable review patch.  If anyone has any objections, please let me know.
> 
> The patch is cleanly applied to 5.10, but it leads to uninit value
> access in rtl_tx_slots_avail().
> 
> 
> 	unsigned int frags;
> 	u32 opts[2];
> 
> 	txd_first = tp->TxDescArray + entry;
> 
> 	if (unlikely(!rtl_tx_slots_avail(tp, frags))) {
>                                              ^^^^^ - USE OF UNINIT VALUE
> 		if (net_ratelimit())
> 			netdev_err(dev, "BUG! Tx Ring full when queue awake!\n");
> 		goto err_stop_0;
> 	}
> 
> 	opts[1] = rtl8169_tx_vlan_tag(skb);
> 	opts[0] = 0;
> 
> 	if (!rtl_chip_supports_csum_v2(tp))
> 		rtl8169_tso_csum_v1(skb, opts);
> 	else if (!rtl8169_tso_csum_v2(tp, skb, opts))
> 		goto err_dma_0;
> 
> 	if (unlikely(rtl8169_tx_map(tp, opts, skb_headlen(skb), skb->data,
> 				    entry, false)))
> 		goto err_dma_0;
> 
> 	txd_first = tp->TxDescArray + entry;
> 
> 	frags = skb_shinfo(skb)->nr_frags;
>         ^^^^^^   - INITIALIZATION IS HERE AFTER THE PATCH
> 
> There is no such problem in upstream because rtl_tx_slots_avail() has no
> nr_frags argument there.
> 
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> --
> Alexey Khoroshilov
> Linux Verification Center, ISPRAS

Looks like the frags argument was removed in commit 83c317d7b36bb (r8169: remove nr_frags argument from rtl_tx_slots_avail), which first appears in linux-5.11.

I dare say it would be safe to replace
 	if (unlikely(!rtl_tx_slots_avail(tp, frags))) {
with
 	if (unlikely(!rtl_tx_slots_avail(tp, MAX_SKB_FRAGS))) {

Best wait for Heiner to confirm though.