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xdp: fix zero-copy frame layout

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xdp_convert_zc_to_xdp_frame() clones an XSK packet into an order-0 page
and advertises PAGE_SIZE as its frame size.  It allows the copied frame
to occupy the page tail needed by skb_shared_info and records zero
headroom even when metadata separates the frame header from packet data.
An AF_XDP zero-copy packet redirected through cpumap can therefore make
the skb overlap skb_shared_info or place it beyond the allocated page.

Limit the copied layout to SKB_WITH_OVERHEAD(PAGE_SIZE) and include the
metadata length in frame headroom.  Redirect callers already handle a
NULL conversion result.

BUG: KASAN: slab-out-of-bounds in skb_gro_receive
Write of size 4 at addr ffff88800cf37004 by task cpumap/1/map:1/146
Call Trace:
 skb_gro_receive (net/core/gro.c:174)
 udp_gro_receive (net/ipv4/udp_offload.c:812)
 inet_gro_receive (net/ipv4/af_inet.c:1539)
 dev_gro_receive (net/core/gro.c:515)
 gro_receive_skb (net/core/gro.c:633)
 cpu_map_kthread_run (kernel/bpf/cpumap.c:395)
 kthread (kernel/kthread.c:436)
 ret_from_fork (arch/x86/kernel/process.c:164)
 ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
Kernel panic - not syncing: KASAN: panic_on_warn set ...

Fixes: b0d1beeff2 ("xdp: implement convert_to_xdp_frame for MEM_TYPE_ZERO_COPY")
Cc: stable@vger.kernel.org
Reported-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Link: https://patch.msgid.link/20260818154516.793517-1-bestswngs@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Weiming Shi
2026-08-18 23:45:15 +08:00
committed by Jakub Kicinski
parent 7c3a1a3481
commit 71283aaa6c
1 changed files with 2 additions and 2 deletions
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4
net/core/xdp.c
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@@ -585,7 +585,7 @@ struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp)
xdp->data - xdp->data_meta;
totsize = xdp->data_end - xdp->data + metasize;
if (sizeof(*xdpf) + totsize > PAGE_SIZE)
if (sizeof(*xdpf) + totsize > SKB_WITH_OVERHEAD(PAGE_SIZE))
return NULL;
page = dev_alloc_page();
@@ -602,7 +602,7 @@ struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp)
xdpf->data = addr + metasize;
xdpf->len = totsize - metasize;
xdpf->headroom = 0;
xdpf->headroom = metasize;
xdpf->metasize = metasize;
xdpf->frame_sz = PAGE_SIZE;
xdpf->mem_type = MEM_TYPE_PAGE_ORDER0;