[PATCH 6.18 233/314] xsk: Fix fragment node deletion to prevent buffer leak

Sasha Levin
2026-03-10T11:29:06Z

From: "Nikhil P. Rao" <nikhil.rao@amd.com>

[ Upstream commit 60abb0ac11dccd6b98fd9182bc5f85b621688861 ]

After commit b692bf9a7543 ("xsk: Get rid of xdp_buff_xsk::xskb_list_node"),
the list_node field is reused for both the xskb pool list and the buffer
free list, this causes a buffer leak as described below.

xp_free() checks if a buffer is already on the free list using
list_empty(&xskb->list_node). When list_del() is used to remove a node
from the xskb pool list, it doesn't reinitialize the node pointers.
This means list_empty() will return false even after the node has been
removed, causing xp_free() to incorrectly skip adding the buffer to the
free list.

Fix this by using list_del_init() instead of list_del() in all fragment
handling paths, this ensures the list node is reinitialized after removal,
allowing the list_empty() to work correctly.

Fixes: b692bf9a7543 ("xsk: Get rid of xdp_buff_xsk::xskb_list_node")
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Nikhil P. Rao <nikhil.rao@amd.com>
Link: https://patch.msgid.link/20260225000456.107806-2-nikhil.rao@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/xdp_sock_drv.h | 6 +++---
net/xdp/xsk.c | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 4f2d3268a6769..99b6c3358e363 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -118,7 +118,7 @@ static inline void xsk_buff_free(struct xdp_buff *xdp)
goto out;

list_for_each_entry_safe(pos, tmp, xskb_list, list_node) {
- list_del(&pos->list_node);
+ list_del_init(&pos->list_node);
xp_free(pos);
}

@@ -153,7 +153,7 @@ static inline struct xdp_buff *xsk_buff_get_frag(const struct xdp_buff *first)
frag = list_first_entry_or_null(&xskb->pool->xskb_list,
struct xdp_buff_xsk, list_node);
if (frag) {
- list_del(&frag->list_node);
+ list_del_init(&frag->list_node);
ret = &frag->xdp;
}

@@ -164,7 +164,7 @@ static inline void xsk_buff_del_frag(struct xdp_buff *xdp)
{
struct xdp_buff_xsk *xskb = container_of(xdp, struct xdp_buff_xsk, xdp);

- list_del(&xskb->list_node);
+ list_del_init(&xskb->list_node);
}

static inline struct xdp_buff *xsk_buff_get_head(struct xdp_buff *first)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 69bbcca8ac753..0d3fc72147f84 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -186,7 +186,7 @@ static int xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
err = __xsk_rcv_zc(xs, pos, len, contd);
if (err)
goto err;
- list_del(&pos->list_node);
+ list_del_init(&pos->list_node);
}

return 0;
--
2.51.0