This is a note to let you know that I've just added the patch titled dpaa_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: dpaa_eth-execute-xdp_do_flush-before-napi_complete_d.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 21bf972b587e05b3d0b294c7fd301ab688052a52 Author: Magnus Karlsson <magnus.karlsson@xxxxxxxxx> Date: Wed Jan 25 08:49:00 2023 +0100 dpaa_eth: execute xdp_do_flush() before napi_complete_done() [ Upstream commit b534013798b77f81a36f36dafd59bab9de837619 ] 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: a1e031ffb422 ("dpaa_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/ Acked-by: Camelia Groza <camelia.groza@xxxxxxx> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c index 685d2d8a3b36..fe5fc2b3406f 100644 --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c @@ -2395,6 +2395,9 @@ static int dpaa_eth_poll(struct napi_struct *napi, int budget) cleaned = qman_p_poll_dqrr(np->p, budget); + if (np->xdp_act & XDP_REDIRECT) + xdp_do_flush(); + if (cleaned < budget) { napi_complete_done(napi, cleaned); qman_p_irqsource_add(np->p, QM_PIRQ_DQRI); @@ -2402,9 +2405,6 @@ static int dpaa_eth_poll(struct napi_struct *napi, int budget) qman_p_irqsource_add(np->p, QM_PIRQ_DQRI); } - if (np->xdp_act & XDP_REDIRECT) - xdp_do_flush(); - return cleaned; }