[PATCH 6.6 046/166] xsk: fix XDP_UMEM_SG_FLAG issues

Greg Kroah-Hartman
2026-04-24T13:35:29Z

From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

[ Upstream commit 93e84fe45b752d17a5a46b306ed78f0133bbc719 ]

Currently xp_assign_dev_shared() is missing XDP_USE_SG being propagated
to flags so set it in order to preserve mtu check that is supposed to be
done only when no multi-buffer setup is in picture.

Also, this flag has the same value as XDP_UMEM_TX_SW_CSUM so we could
get unexpected SG setups for software Tx checksums. Since csum flag is
UAPI, modify value of XDP_UMEM_SG_FLAG.

Fixes: d609f3d228a8 ("xsk: add multi-buffer support for sockets sharing umem")
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://patch.msgid.link/20260402154958.562179-4-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/xdp_sock.h | 2 +-
net/xdp/xsk_buff_pool.c | 4 ++++
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 660c22521a292..84ff9bb4bfae4 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -14,7 +14,7 @@
#include <linux/mm.h>
#include <net/sock.h>

-#define XDP_UMEM_SG_FLAG (1 << 1)
+#define XDP_UMEM_SG_FLAG BIT(3)

struct net_device;
struct xsk_queue;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 6789d99fd99e0..52c4204bc224e 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -236,6 +236,10 @@ int xp_assign_dev_shared(struct xsk_buff_pool *pool, struct xdp_sock *umem_xs,
return -EINVAL;

flags = umem->zc ? XDP_ZEROCOPY : XDP_COPY;
+
+ if (umem->flags & XDP_UMEM_SG_FLAG)
+ flags |= XDP_USE_SG;
+
if (umem_xs->pool->uses_need_wakeup)
flags |= XDP_USE_NEED_WAKEUP;

--
2.53.0