Patch "dpaa2-eth: execute xdp_do_flush() before napi_complete_done()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    dpaa2-eth: execute xdp_do_flush() before napi_complete_done()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dpaa2-eth-execute-xdp_do_flush-before-napi_complete_.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a179c24374a651a706cd51f38dff0bcb894b001b
Author: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Date:   Wed Jan 25 08:49:01 2023 +0100

    dpaa2-eth: execute xdp_do_flush() before napi_complete_done()
    
    [ Upstream commit a3191c4d86c5d3bd35b00dfde6910b88391436a0 ]
    
    Make sure that xdp_do_flush() is always executed before
    napi_complete_done(). This is important for two reasons. First, a
    redirect to an XSKMAP assumes that a call to xdp_do_redirect() from
    napi context X on CPU Y will be followed by a xdp_do_flush() from the
    same napi context and CPU. This is not guaranteed if the
    napi_complete_done() is executed before xdp_do_flush(), as it tells
    the napi logic that it is fine to schedule napi context X on another
    CPU. Details from a production system triggering this bug using the
    veth driver can be found following the first link below.
    
    The second reason is that the XDP_REDIRECT logic in itself relies on
    being inside a single NAPI instance through to the xdp_do_flush() call
    for RCU protection of all in-kernel data structures. Details can be
    found in the second link below.
    
    Fixes: d678be1dc1ec ("dpaa2-eth: add XDP_REDIRECT support")
    Signed-off-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
    Acked-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20221220185903.1105011-1-sbohrer@xxxxxxxxxxxxxx
    Link: https://lore.kernel.org/all/20210624160609.292325-1-toke@xxxxxxxxxx/
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index 5899139aec97..c48d41093651 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -1597,10 +1597,15 @@ static int dpaa2_eth_poll(struct napi_struct *napi, int budget)
 		if (rx_cleaned >= budget ||
 		    txconf_cleaned >= DPAA2_ETH_TXCONF_PER_NAPI) {
 			work_done = budget;
+			if (ch->xdp.res & XDP_REDIRECT)
+				xdp_do_flush();
 			goto out;
 		}
 	} while (store_cleaned);
 
+	if (ch->xdp.res & XDP_REDIRECT)
+		xdp_do_flush();
+
 	/* We didn't consume the entire budget, so finish napi and
 	 * re-enable data availability notifications
 	 */
@@ -1625,9 +1630,7 @@ static int dpaa2_eth_poll(struct napi_struct *napi, int budget)
 		txc_fq->dq_bytes = 0;
 	}
 
-	if (ch->xdp.res & XDP_REDIRECT)
-		xdp_do_flush_map();
-	else if (rx_cleaned && ch->xdp.res & XDP_TX)
+	if (rx_cleaned && ch->xdp.res & XDP_TX)
 		dpaa2_eth_xdp_tx_flush(priv, ch, &priv->fq[flowid]);
 
 	return work_done;