memory leak in qdisc_create_dflt

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 9ebcfadb Linux 5.8-rc3
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1577525b100000
kernel config: https://syzkaller.appspot.com/x/.config?x=5ee23b9caef4e07a
dashboard link: https://syzkaller.appspot.com/bug?extid=d411cff6ab29cc2c311b
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10e579e3100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1007c45b100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d411cf...@syzkaller.appspotmail.com

BUG: memory leak
unreferenced object 0xffff888115aa8c00 (size 512):
comm "syz-executor530", pid 6646, jiffies 4294943517 (age 13.870s)
hex dump (first 32 bytes):
a0 0c be 82 ff ff ff ff f0 0b be 82 ff ff ff ff ................
04 00 00 00 e8 03 00 00 40 c6 72 84 ff ff ff ff ........@.r.....
backtrace:
[<00000000ead56edd>] kmalloc_node include/linux/slab.h:578 [inline]
[<00000000ead56edd>] kzalloc_node include/linux/slab.h:680 [inline]
[<00000000ead56edd>] qdisc_alloc+0x45/0x260 net/sched/sch_generic.c:818
[<000000002852d256>] qdisc_create_dflt+0x3d/0x170 net/sched/sch_generic.c:893
[<000000002108f663>] atm_tc_init+0x96/0x150 net/sched/sch_atm.c:551
[<000000000988e5f0>] qdisc_create+0x1ae/0x670 net/sched/sch_api.c:1246
[<00000000c8befd49>] tc_modify_qdisc+0x198/0xb10 net/sched/sch_api.c:1662
[<00000000b014fe08>] rtnetlink_rcv_msg+0x17e/0x460 net/core/rtnetlink.c:5460
[<00000000da7a0de1>] netlink_rcv_skb+0x5b/0x180 net/netlink/af_netlink.c:2469
[<0000000069fa5fbe>] netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
[<0000000069fa5fbe>] netlink_unicast+0x2b6/0x3c0 net/netlink/af_netlink.c:1329
[<0000000049c303c5>] netlink_sendmsg+0x2ba/0x570 net/netlink/af_netlink.c:1918
[<0000000017755dda>] sock_sendmsg_nosec net/socket.c:652 [inline]
[<0000000017755dda>] sock_sendmsg+0x4c/0x60 net/socket.c:672
[<00000000294b696a>] ____sys_sendmsg+0x118/0x2f0 net/socket.c:2352
[<00000000eb7a1f59>] ___sys_sendmsg+0x81/0xc0 net/socket.c:2406
[<00000000ba1066c9>] __sys_sendmmsg+0xda/0x230 net/socket.c:2496
[<0000000082fdecc3>] __do_sys_sendmmsg net/socket.c:2525 [inline]
[<0000000082fdecc3>] __se_sys_sendmmsg net/socket.c:2522 [inline]
[<0000000082fdecc3>] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2522
[<000000009da3552a>] do_syscall_64+0x4c/0xe0 arch/x86/entry/common.c:359
[<00000000b46d0fac>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff888115aa8a00 (size 512):
comm "syz-executor530", pid 6647, jiffies 4294944100 (age 8.040s)
hex dump (first 32 bytes):
a0 0c be 82 ff ff ff ff f0 0b be 82 ff ff ff ff ................
04 00 00 00 e8 03 00 00 40 c6 72 84 ff ff ff ff ........@.r.....
backtrace:
[<00000000ead56edd>] kmalloc_node include/linux/slab.h:578 [inline]
[<00000000ead56edd>] kzalloc_node include/linux/slab.h:680 [inline]
[<00000000ead56edd>] qdisc_alloc+0x45/0x260 net/sched/sch_generic.c:818
[<000000002852d256>] qdisc_create_dflt+0x3d/0x170 net/sched/sch_generic.c:893
[<000000002108f663>] atm_tc_init+0x96/0x150 net/sched/sch_atm.c:551
[<000000000988e5f0>] qdisc_create+0x1ae/0x670 net/sched/sch_api.c:1246
[<00000000c8befd49>] tc_modify_qdisc+0x198/0xb10 net/sched/sch_api.c:1662
[<00000000b014fe08>] rtnetlink_rcv_msg+0x17e/0x460 net/core/rtnetlink.c:5460
[<00000000da7a0de1>] netlink_rcv_skb+0x5b/0x180 net/netlink/af_netlink.c:2469
[<0000000069fa5fbe>] netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
[<0000000069fa5fbe>] netlink_unicast+0x2b6/0x3c0 net/netlink/af_netlink.c:1329
[<0000000049c303c5>] netlink_sendmsg+0x2ba/0x570 net/netlink/af_netlink.c:1918
[<0000000017755dda>] sock_sendmsg_nosec net/socket.c:652 [inline]
[<0000000017755dda>] sock_sendmsg+0x4c/0x60 net/socket.c:672
[<00000000294b696a>] ____sys_sendmsg+0x118/0x2f0 net/socket.c:2352
[<00000000eb7a1f59>] ___sys_sendmsg+0x81/0xc0 net/socket.c:2406
[<00000000ba1066c9>] __sys_sendmmsg+0xda/0x230 net/socket.c:2496
[<0000000082fdecc3>] __do_sys_sendmmsg net/socket.c:2525 [inline]
[<0000000082fdecc3>] __se_sys_sendmmsg net/socket.c:2522 [inline]
[<0000000082fdecc3>] __x64_sys_sendmmsg+0x24/0x30 net/socket.c:2522
[<000000009da3552a>] do_syscall_64+0x4c/0xe0 arch/x86/entry/common.c:359
[<00000000b46d0fac>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



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[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: syzbot+d411cf...@syzkaller.appspotmail.com

Tested on:

commit: c2bbfeb1 net_sched: fix a memory leak in atm_tc_init()
git tree: https://github.com/congwang/linux.git net
kernel config: https://syzkaller.appspot.com/x/.config?x=804c47e6e1f474ed

dashboard link: https://syzkaller.appspot.com/bug?extid=d411cff6ab29cc2c311b
compiler: gcc (GCC) 10.1.0-syz 20200507

Note: testing is done by a robot and is best-effort only.