pkt_sched: sch_qfq: fix qfq_change_class() error path

If qfq_change_class() is unable to allocate memory for qfq_aggregate,
it frees the class that has been inserted in the class hash table,
but does not unhash it.

Defer the insertion after the problematic allocation.

BUG: KASAN: use-after-free in hlist_add_head include/linux/list.h:884 [inline]
BUG: KASAN: use-after-free in qdisc_class_hash_insert+0x200/0x210 net/sched/sch_api.c:731
Write of size 8 at addr ffff88814a534f10 by task syz-executor.4/31478

CPU: 0 PID: 31478 Comm: syz-executor.4 Not tainted 5.13.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:233
 __kasan_report mm/kasan/report.c:419 [inline]
 kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:436
 hlist_add_head include/linux/list.h:884 [inline]
 qdisc_class_hash_insert+0x200/0x210 net/sched/sch_api.c:731
 qfq_change_class+0x96c/0x1990 net/sched/sch_qfq.c:489
 tc_ctl_tclass+0x514/0xe50 net/sched/sch_api.c:2113
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5564
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1929
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdc7b5f0188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00007fdc7b5f01d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffcf7310b3f R14: 00007fdc7b5f0300 R15: 0000000000022000

Allocated by task 31445:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:428 [inline]
 ____kasan_kmalloc mm/kasan/common.c:507 [inline]
 ____kasan_kmalloc mm/kasan/common.c:466 [inline]
 __kasan_kmalloc+0x9b/0xd0 mm/kasan/common.c:516
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:686 [inline]
 qfq_change_class+0x705/0x1990 net/sched/sch_qfq.c:464
 tc_ctl_tclass+0x514/0xe50 net/sched/sch_api.c:2113
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5564
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1929
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 31445:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
 ____kasan_slab_free mm/kasan/common.c:360 [inline]
 ____kasan_slab_free mm/kasan/common.c:325 [inline]
 __kasan_slab_free+0xfb/0x130 mm/kasan/common.c:368
 kasan_slab_free include/linux/kasan.h:212 [inline]
 slab_free_hook mm/slub.c:1583 [inline]
 slab_free_freelist_hook+0xdf/0x240 mm/slub.c:1608
 slab_free mm/slub.c:3168 [inline]
 kfree+0xe5/0x7f0 mm/slub.c:4212
 qfq_change_class+0x10fb/0x1990 net/sched/sch_qfq.c:518
 tc_ctl_tclass+0x514/0xe50 net/sched/sch_api.c:2113
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5564
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1929
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:674
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2350
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2404
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2433
 do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88814a534f00
 which belongs to the cache kmalloc-128 of size 128
The buggy address is located 16 bytes inside of
 128-byte region [ffff88814a534f00, ffff88814a534f80)
The buggy address belongs to the page:
page:ffffea0005294d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14a534
flags: 0x57ff00000000200(slab|node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000200 ffffea00004fee00 0000000600000006 ffff8880110418c0
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 29797, ts 604817765317, free_ts 604810151744
 prep_new_page mm/page_alloc.c:2358 [inline]
 get_page_from_freelist+0x1033/0x2b60 mm/page_alloc.c:3994
 __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5200
 alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
 alloc_slab_page mm/slub.c:1646 [inline]
 allocate_slab+0x2c5/0x4c0 mm/slub.c:1786
 new_slab mm/slub.c:1849 [inline]
 new_slab_objects mm/slub.c:2595 [inline]
 ___slab_alloc+0x4a1/0x810 mm/slub.c:2758
 __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2798
 slab_alloc_node mm/slub.c:2880 [inline]
 slab_alloc mm/slub.c:2922 [inline]
 __kmalloc+0x315/0x330 mm/slub.c:4050
 kmalloc include/linux/slab.h:561 [inline]
 kzalloc include/linux/slab.h:686 [inline]
 __register_sysctl_table+0x112/0x1090 fs/proc/proc_sysctl.c:1318
 mpls_dev_sysctl_register+0x1b7/0x2d0 net/mpls/af_mpls.c:1421
 mpls_add_dev net/mpls/af_mpls.c:1472 [inline]
 mpls_dev_notify+0x214/0x8b0 net/mpls/af_mpls.c:1588
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:83
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:2121
 call_netdevice_notifiers_extack net/core/dev.c:2133 [inline]
 call_netdevice_notifiers net/core/dev.c:2147 [inline]
 register_netdevice+0x106b/0x1500 net/core/dev.c:10312
 veth_newlink+0x585/0xac0 drivers/net/veth.c:1547
 __rtnl_newlink+0x1062/0x1710 net/core/rtnetlink.c:3452
 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3500
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1298 [inline]
 free_pcp_prepare+0x223/0x300 mm/page_alloc.c:1342
 free_unref_page_prepare mm/page_alloc.c:3250 [inline]
 free_unref_page+0x12/0x1d0 mm/page_alloc.c:3298
 __vunmap+0x783/0xb60 mm/vmalloc.c:2566
 free_work+0x58/0x70 mm/vmalloc.c:80
 process_one_work+0x98d/0x1600 kernel/workqueue.c:2276
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2422
 kthread+0x3b1/0x4a0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Memory state around the buggy address:
 ffff88814a534e00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88814a534e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88814a534f00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff88814a534f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88814a535000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Fixes: 462dbc9101 ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_qfq.c

@@ -485,11 +485,6 @@ static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
 
 	if (cl->qdisc != &noop_qdisc)
 		qdisc_hash_add(cl->qdisc, true);
-	sch_tree_lock(sch);
-	qdisc_class_hash_insert(&q->clhash, &cl->common);
-	sch_tree_unlock(sch);
-
-	qdisc_class_hash_grow(sch, &q->clhash);
 
 set_change_agg:
 	sch_tree_lock(sch);
@@ -507,8 +502,11 @@ set_change_agg:
 	}
 	if (existing)
 		qfq_deact_rm_from_agg(q, cl);
+	else
+		qdisc_class_hash_insert(&q->clhash, &cl->common);
 	qfq_add_to_agg(q, new_agg, cl);
 	sch_tree_unlock(sch);
+	qdisc_class_hash_grow(sch, &q->clhash);
 
 	*arg = (unsigned long)cl;
 	return 0;