From: Shawn Bohrer sbohrer@cloudflare.com
[ Upstream commit 7c10131803e45269ddc6c817f19ed649110f3cae ]
Commit 718a18a0c8a6 ("veth: Rework veth_xdp_rcv_skb in order to accept non-linear skb") introduced a bug where it tried to use pskb_expand_head() if the headroom was less than XDP_PACKET_HEADROOM. This however uses kmalloc to expand the head, which will later allow consume_skb() to free the skb while is it still in use by AF_XDP.
Previously if the headroom was less than XDP_PACKET_HEADROOM we continued on to allocate a new skb from pages so this restores that behavior.
BUG: KASAN: use-after-free in __xsk_rcv+0x18d/0x2c0 Read of size 78 at addr ffff888976250154 by task napi/iconduit-g/148640
CPU: 5 PID: 148640 Comm: napi/iconduit-g Kdump: loaded Tainted: G O 6.1.4-cloudflare-kasan-2023.1.2 #1 Hardware name: Quanta Computer Inc. QuantaPlex T41S-2U/S2S-MB, BIOS S2S_3B10.03 06/21/2018 Call Trace: <TASK> dump_stack_lvl+0x34/0x48 print_report+0x170/0x473 ? __xsk_rcv+0x18d/0x2c0 kasan_report+0xad/0x130 ? __xsk_rcv+0x18d/0x2c0 kasan_check_range+0x149/0x1a0 memcpy+0x20/0x60 __xsk_rcv+0x18d/0x2c0 __xsk_map_redirect+0x1f3/0x490 ? veth_xdp_rcv_skb+0x89c/0x1ba0 [veth] xdp_do_redirect+0x5ca/0xd60 veth_xdp_rcv_skb+0x935/0x1ba0 [veth] ? __netif_receive_skb_list_core+0x671/0x920 ? veth_xdp+0x670/0x670 [veth] veth_xdp_rcv+0x304/0xa20 [veth] ? do_xdp_generic+0x150/0x150 ? veth_xdp_rcv_one+0xde0/0xde0 [veth] ? _raw_spin_lock_bh+0xe0/0xe0 ? newidle_balance+0x887/0xe30 ? __perf_event_task_sched_in+0xdb/0x800 veth_poll+0x139/0x571 [veth] ? veth_xdp_rcv+0xa20/0xa20 [veth] ? _raw_spin_unlock+0x39/0x70 ? finish_task_switch.isra.0+0x17e/0x7d0 ? __switch_to+0x5cf/0x1070 ? __schedule+0x95b/0x2640 ? io_schedule_timeout+0x160/0x160 __napi_poll+0xa1/0x440 napi_threaded_poll+0x3d1/0x460 ? __napi_poll+0x440/0x440 ? __kthread_parkme+0xc6/0x1f0 ? __napi_poll+0x440/0x440 kthread+0x2a2/0x340 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x22/0x30 </TASK>
Freed by task 148640: kasan_save_stack+0x23/0x50 kasan_set_track+0x21/0x30 kasan_save_free_info+0x2a/0x40 ____kasan_slab_free+0x169/0x1d0 slab_free_freelist_hook+0xd2/0x190 __kmem_cache_free+0x1a1/0x2f0 skb_release_data+0x449/0x600 consume_skb+0x9f/0x1c0 veth_xdp_rcv_skb+0x89c/0x1ba0 [veth] veth_xdp_rcv+0x304/0xa20 [veth] veth_poll+0x139/0x571 [veth] __napi_poll+0xa1/0x440 napi_threaded_poll+0x3d1/0x460 kthread+0x2a2/0x340 ret_from_fork+0x22/0x30
The buggy address belongs to the object at ffff888976250000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 340 bytes inside of 2048-byte region [ffff888976250000, ffff888976250800)
The buggy address belongs to the physical page: page:00000000ae18262a refcount:2 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x976250 head:00000000ae18262a order:3 compound_mapcount:0 compound_pincount:0 flags: 0x2ffff800010200(slab|head|node=0|zone=2|lastcpupid=0x1ffff) raw: 002ffff800010200 0000000000000000 dead000000000122 ffff88810004cf00 raw: 0000000000000000 0000000080080008 00000002ffffffff 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff888976250000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888976250080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888976250100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff888976250180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888976250200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
Fixes: 718a18a0c8a6 ("veth: Rework veth_xdp_rcv_skb in order to accept non-linear skb") Signed-off-by: Shawn Bohrer sbohrer@cloudflare.com Acked-by: Lorenzo Bianconi lorenzo@kernel.org Acked-by: Toshiaki Makita toshiaki.makita1@gmail.com Acked-by: Toke Høiland-Jørgensen toke@kernel.org Link: https://lore.kernel.org/r/20230314153351.2201328-1-sbohrer@cloudflare.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/veth.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/net/veth.c b/drivers/net/veth.c index dfc7d87fad59f..30ae6695f8643 100644 --- a/drivers/net/veth.c +++ b/drivers/net/veth.c @@ -701,7 +701,8 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq, u32 frame_sz;
if (skb_shared(skb) || skb_head_is_locked(skb) || - skb_shinfo(skb)->nr_frags) { + skb_shinfo(skb)->nr_frags || + skb_headroom(skb) < XDP_PACKET_HEADROOM) { u32 size, len, max_head_size, off; struct sk_buff *nskb; struct page *page; @@ -766,9 +767,6 @@ static int veth_convert_skb_to_xdp_buff(struct veth_rq *rq,
consume_skb(skb); skb = nskb; - } else if (skb_headroom(skb) < XDP_PACKET_HEADROOM && - pskb_expand_head(skb, VETH_XDP_HEADROOM, 0, GFP_ATOMIC)) { - goto drop; }
/* SKB "head" area always have tailroom for skb_shared_info */