[PATCH net v4] net: mvneta: clear XDP pfmemalloc flag between frames

mvneta_swbm_add_rx_fragment() sets XDP_FLAGS_FRAGS_PF_MEMALLOC on the
xdp_buff when a fragment page is a pfmemalloc one (page under memory
pressure). The xdp_buff is reused for the next frame, but only the
XDP_FLAGS_HAS_FRAGS bit was cleared at frame start, so the pfmemalloc
bit leaked from one frame into the following ones. mvneta_swbm_build_skb()
propagates the flag to skb->pfmemalloc through xdp_update_skb_frags_info(),
so the skb of a subsequent fragmented frame could be wrongly marked as
pfmemalloc even if none of its pages are under pressure.

Clear all the xdp_buff flags in mvneta_swbm_rx_frame(), which is invoked
for each new frame, instead of just the XDP_FLAGS_HAS_FRAGS bit.

Fixes: ed7a58cb40bd ("net: marvell: rely on xdp_update_skb_shared_info utility routine")
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Lorenzo Bianconi <redacted>
---
Changes in v4:
- Rename xdp_reinit_buf() in xdp_reinit_buff().
- Link to v3: https://lore.kernel.org/r/20260928-mvneta-xdp-clear-frag-fix-v3-1-af4a51499eaf@oss.qualcomm.com (local)

Changes in v3:
- Rename xdp_buff_clear_flags() in xdp_reinit_buf().
- Link to v2: https://lore.kernel.org/r/20260923-mvneta-xdp-clear-frag-fix-v2-1-298693a7ea6b@oss.qualcomm.com (local)

Changes in v2:
- Introduce xdp_buff_clear_flags() utility routine.
- Link to v1: https://lore.kernel.org/r/20260920-mvneta-xdp-clear-frag-fix-v1-1-d7efadecf959@oss.qualcomm.com (local)
---
 drivers/net/ethernet/marvell/mvneta.c | 2 +-
 include/net/xdp.h                     | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 543e566425c1..4f479b6f731e 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c

@@ -2340,7 +2340,7 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
 
 	/* Prefetch header */
 	prefetch(data);
-	xdp_buff_clear_frags_flag(xdp);
+	xdp_reinit_buff(xdp);
 	xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
 			 data_len, true);
 }

diff --git a/include/net/xdp.h b/include/net/xdp.h
index aa742f413c35..07231adfb5f8 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h

@@ -106,6 +106,11 @@ struct xdp_buff {
 	};
 };
 
+static __always_inline void xdp_reinit_buff(struct xdp_buff *xdp)
+{
+	xdp->flags = 0;
+}
+
 static __always_inline bool xdp_buff_has_frags(const struct xdp_buff *xdp)
 {
 	return !!(xdp->flags & XDP_FLAGS_HAS_FRAGS);

---
base-commit: 54518e0e827f4ca9229ae657022c60bf60f5c1bf
change-id: 20260919-mvneta-xdp-clear-frag-fix-7ac691e1659b

Best regards,
-- 
Lorenzo Bianconi [off-list ref]