Commit db359fccf2 ("mm: introduce a new page type for page pool in
page type") added a page_type field to struct net_iov at the same
offset as struct page::page_type, so that page_pool_set_pp_info() can
call __SetPageNetpp() uniformly on both pages and net_iovs.
The page-type API requires the field to hold the UINT_MAX "no type"
sentinel before a type can be set; for real struct page that invariant
is established by the page allocator on free. struct net_iov is not
allocated through the page allocator, so the field is left as zero
(io_uring zcrx, which uses __GFP_ZERO) or as slab garbage (devmem,
which uses kvmalloc_objs() without zeroing). When the page pool then
calls page_pool_set_pp_info() on a freshly-bound niov,
__SetPageNetpp()'s VM_BUG_ON_PAGE(page->page_type != UINT_MAX) fires
and the kernel BUGs. Triggered in selftests by io_uring zcrx setup
through the fbnic queue restart path:
kernel BUG at ./include/linux/page-flags.h:1062!
RIP: 0010:page_pool_set_pp_info (./include/linux/page-flags.h:1062
net/core/page_pool.c:716)
Call Trace:
<TASK>
net_mp_niov_set_page_pool (net/core/page_pool.c:1360)
io_pp_zc_alloc_netmems (io_uring/zcrx.c:1089 io_uring/zcrx.c:1110)
fbnic_fill_bdq (./include/net/page_pool/helpers.h:160
drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:906)
__fbnic_nv_restart (drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:2470
drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:2874)
fbnic_queue_start (drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:2903)
netdev_rx_queue_reconfig (net/core/netdev_rx_queue.c:137)
__netif_mp_open_rxq (net/core/netdev_rx_queue.c:234)
io_register_zcrx (io_uring/zcrx.c:818 io_uring/zcrx.c:903)
__io_uring_register (io_uring/register.c:931)
__do_sys_io_uring_register (io_uring/register.c:1029)
do_syscall_64 (arch/x86/entry/syscall_64.c:63
arch/x86/entry/syscall_64.c:94)
</TASK>
The same path is reachable through devmem dmabuf binding via
netdev_nl_bind_rx_doit() -> net_devmem_bind_dmabuf_to_queue().
Add a net_iov_init() helper that stamps ->owner, ->type and the
->page_type sentinel, and use it from both the devmem and io_uring
zcrx niov init loops.
Fixes: db359fccf2 ("mm: introduce a new page type for page pool in page type")
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Acked-by: Byungchul Park <byungchul@sk.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/20260428025320.853452-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
735a309b4b