net: ti: icssg-prueth: fix missing data copy and wrong recycle in ZC RX dispatch

[PATCH] net: ti: icssg-prueth: fix missing data copy and wrong recycle in ZC RX dispatch

Posted by David Carlier 1 week, 1 day ago

emac_dispatch_skb_zc() allocates a new skb via napi_alloc_skb() but
never copies the packet data from the XDP buffer into it. The skb is
passed up the stack containing uninitialized heap memory instead of
the actual received packet, leaking kernel heap contents to userspace.

Copy the received packet data from the XDP buffer into the skb using
skb_copy_to_linear_data().

Additionally, remove the skb_mark_for_recycle() call since the skb is
backed by the NAPI page frag allocator, not page_pool. Marking a
non-page_pool skb for recycle causes the free path to return pages to
a page_pool that does not own them, corrupting page_pool state.

The non-ZC path (emac_rx_packet) does not have these issues because it
uses napi_build_skb() to wrap the existing page_pool page directly,
requiring no copy, and correctly marks for recycle since the page comes
from page_pool_dev_alloc_pages().

Fixes: 7a64bb388df3 ("net: ti: icssg-prueth: Add AF_XDP zero copy for RX")
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 drivers/net/ethernet/ti/icssg/icssg_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
index fd4e7622f123..a28a608f9bf4 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_common.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
@@ -902,6 +902,7 @@ static void emac_dispatch_skb_zc(struct prueth_emac *emac, struct xdp_buff *xdp,
 
 	skb_reserve(skb, headroom);
 	skb_put(skb, pkt_len);
+	skb_copy_to_linear_data(skb, xdp->data, pkt_len);
 	skb->dev = ndev;
 
 	/* RX HW timestamp */
@@ -912,7 +913,6 @@ static void emac_dispatch_skb_zc(struct prueth_emac *emac, struct xdp_buff *xdp,
 		skb->offload_fwd_mark = emac->offload_fwd_mark;
 	skb->protocol = eth_type_trans(skb, ndev);
 
-	skb_mark_for_recycle(skb);
 	napi_gro_receive(&emac->napi_rx, skb);
 	ndev->stats.rx_bytes += pkt_len;
 	ndev->stats.rx_packets++;
-- 
2.53.0

Re: [PATCH] net: ti: icssg-prueth: fix missing data copy and wrong recycle in ZC RX dispatch

Posted by Simon Horman 6 days, 13 hours ago

+ Meghana Malladi

On Wed, Mar 25, 2026 at 12:51:30PM +0000, David Carlier wrote:
> emac_dispatch_skb_zc() allocates a new skb via napi_alloc_skb() but
> never copies the packet data from the XDP buffer into it. The skb is
> passed up the stack containing uninitialized heap memory instead of
> the actual received packet, leaking kernel heap contents to userspace.
> 
> Copy the received packet data from the XDP buffer into the skb using
> skb_copy_to_linear_data().
> 
> Additionally, remove the skb_mark_for_recycle() call since the skb is
> backed by the NAPI page frag allocator, not page_pool. Marking a
> non-page_pool skb for recycle causes the free path to return pages to
> a page_pool that does not own them, corrupting page_pool state.
> 
> The non-ZC path (emac_rx_packet) does not have these issues because it
> uses napi_build_skb() to wrap the existing page_pool page directly,
> requiring no copy, and correctly marks for recycle since the page comes
> from page_pool_dev_alloc_pages().
> 
> Fixes: 7a64bb388df3 ("net: ti: icssg-prueth: Add AF_XDP zero copy for RX")
> Signed-off-by: David Carlier <devnexen@gmail.com>
> ---
>  drivers/net/ethernet/ti/icssg/icssg_common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Hi David,

Thanks for the update.
My understanding is that this addresses the review of v1.

Reviewed-by: Simon Horman <horms@kernel.org>

v1: https://lore.kernel.org/all/20260324211402.342474-1-devnexen@gmail.com/

Some points to keep in mind for the future:

* Please include a version number in the subject when posting versions >
  This helps a lot in tracking things.

  Subject: [PATCH v2] ...

* Please include the target tree. As a fix for code, which I asusme
  is present in net, in this case that would be the net tree.

  Subject: [PATCH net v2] ...

  Otherwise it would probably be the net-next tree.

* Please CC all relevant parties. In this case that would
  include Meghana as he provided review of v1.

* Please consider including a changelog, along with links to earlier
  versions below the scissors ("---")

* b4 can help with most of these things

* More information on the Netdev development process can be found at
  https://docs.kernel.org/process/maintainer-netdev.html

...

Re: [PATCH] net: ti: icssg-prueth: fix missing data copy and wrong recycle in ZC RX dispatch

Posted by David CARLIER 6 days, 13 hours ago

Hi Simon and thanks for the feedback, will keep this in mind. Cheers !

On Fri, 27 Mar 2026 at 10:29, Simon Horman <horms@kernel.org> wrote:
>
> + Meghana Malladi
>
> On Wed, Mar 25, 2026 at 12:51:30PM +0000, David Carlier wrote:
> > emac_dispatch_skb_zc() allocates a new skb via napi_alloc_skb() but
> > never copies the packet data from the XDP buffer into it. The skb is
> > passed up the stack containing uninitialized heap memory instead of
> > the actual received packet, leaking kernel heap contents to userspace.
> >
> > Copy the received packet data from the XDP buffer into the skb using
> > skb_copy_to_linear_data().
> >
> > Additionally, remove the skb_mark_for_recycle() call since the skb is
> > backed by the NAPI page frag allocator, not page_pool. Marking a
> > non-page_pool skb for recycle causes the free path to return pages to
> > a page_pool that does not own them, corrupting page_pool state.
> >
> > The non-ZC path (emac_rx_packet) does not have these issues because it
> > uses napi_build_skb() to wrap the existing page_pool page directly,
> > requiring no copy, and correctly marks for recycle since the page comes
> > from page_pool_dev_alloc_pages().
> >
> > Fixes: 7a64bb388df3 ("net: ti: icssg-prueth: Add AF_XDP zero copy for RX")
> > Signed-off-by: David Carlier <devnexen@gmail.com>
> > ---
> >  drivers/net/ethernet/ti/icssg/icssg_common.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Hi David,
>
> Thanks for the update.
> My understanding is that this addresses the review of v1.
>
> Reviewed-by: Simon Horman <horms@kernel.org>
>
> v1: https://lore.kernel.org/all/20260324211402.342474-1-devnexen@gmail.com/
>
> Some points to keep in mind for the future:
>
> * Please include a version number in the subject when posting versions >
>   This helps a lot in tracking things.
>
>   Subject: [PATCH v2] ...
>
> * Please include the target tree. As a fix for code, which I asusme
>   is present in net, in this case that would be the net tree.
>
>   Subject: [PATCH net v2] ...
>
>   Otherwise it would probably be the net-next tree.
>
> * Please CC all relevant parties. In this case that would
>   include Meghana as he provided review of v1.
>
> * Please consider including a changelog, along with links to earlier
>   versions below the scissors ("---")
>
> * b4 can help with most of these things
>
> * More information on the Netdev development process can be found at
>   https://docs.kernel.org/process/maintainer-netdev.html
>
> ...