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Sashiko AI review found 2 potential issue(s) to consider: > > Pre-existing issues: > - [High] Zero-copy drivers unconditionally parse XDP TX metadata ignoring the XDP_TX_METADATA option flag. > - [High] The stmmac driver drops AF_XDP TX frames without generating completions when the frame length exceeds max_sdu, causing the AF_XDP completion queue (CQ) to permanently desynchronize. > -- > > --- Patch [6]: [PATCH net 6/6] xsk: validate metadata when processing requests --- > commit 8967b4032038ba439c0a13ce2dc4cab303b87c2e > Author: Stanislav Fomichev > > xsk: validate metadata when processing requests > > The zero-copy path validates TX metadata while obtaining the descriptor > context, then reads it again later when preparing the hardware request. > Validate the metadata in xsk_tx_metadata_request() and use the resulting > flags snapshot for every feature check. > > > diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c > > index 5a18d00deb4f4..7b6cdc037c00f 100644 > > --- a/drivers/net/ethernet/intel/igc/igc_main.c > > +++ b/drivers/net/ethernet/intel/igc/igc_main.c > > @@ -3082,7 +3082,7 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring) > > meta_req.tx_buffer = bi; > > meta_req.meta = meta; > > meta_req.used_desc = 0; > > - xsk_tx_metadata_request(&meta, &igc_xsk_tx_metadata_ops, > > + xsk_tx_metadata_request(pool, &meta, &igc_xsk_tx_metadata_ops, > > &meta_req); > > [Severity: High] > This is a pre-existing issue, but do the zero-copy drivers unconditionally > parse XDP TX metadata while ignoring the XDP_TX_METADATA option flag? > > Looking at igc_xdp_xmit_zc() (and similarly in mlx5e_xsk_tx() and > stmmac_xdp_xmit_zc()), the zero-copy path reads metadata directly without > checking xdp_desc.options: > > meta = xsk_buff_get_metadata(pool, xdp_desc.addr); > > If an application sends a standard AF_XDP packet without requesting metadata > (by clearing the XDP_TX_METADATA flag), the driver ignores desc->options and > unconditionally reads the metadata memory. Since the memory might contain > stale data, meta->flags could contain valid but bogus bits. > > Could this trigger unintended hardware offloads, causing data corruption > (bogus checksum offsets) or TX queue stalls (bogus launch times)? That seems like a valid pre-existing issue, will address separately. > [ ... ] > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > index 3f5111969c414..eb666b0bcdd22 100644 > > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > @@ -2747,8 +2747,8 @@ static bool stmmac_xdp_xmit_zc(struct stmmac_priv *priv, u32 queue, u32 budget) > > meta_req.set_ic = &set_ic; > > meta_req.tbs = tx_q->tbs; > > meta_req.edesc = &tx_q->dma_entx[entry]; > > - xsk_tx_metadata_request(&meta, &stmmac_xsk_tx_metadata_ops, > > - &meta_req); > > + xsk_tx_metadata_request(pool, &meta, > > + &stmmac_xsk_tx_metadata_ops, &meta_req); > > [Severity: High] > This isn't a bug introduced by this patch, but does stmmac_xdp_xmit_zc() > permanently desynchronize the AF_XDP completion queue when dropping oversized > frames? > > Earlier in stmmac_xdp_xmit_zc(), if the frame length exceeds max_sdu, the > descriptor is dropped via continue without issuing an XSK completion or > posting a dummy hardware descriptor: > > if (priv->est && priv->est->enable && > priv->est->max_sdu[queue] && > xdp_desc.len > priv->est->max_sdu[queue]) { > priv->xstats.max_sdu_txq_drop[queue]++; > continue; > } > > Since xsk_tx_peek_desc() reserves a slot in the AF_XDP completion queue (CQ), > dropping the frame skips the hardware descriptor setup, and no completion > interrupt is generated for this packet. > > When a subsequent packet completes, xsk_tx_completed() will advance the CQ > producer. Because CQ entries are positional, would user space receive the > address of the dropped packet as a completion instead of the actually > completed packet, permanently leaking descriptors? Hmm, good point, will send a patch separately to reorder xsk_tx_peek_desc and max_sdu check.