CVE-2021-47418

In the Linux kernel, the following vulnerability has been resolved:
net_sched: fix NULL deref in fifo_set_limit() syzbot reported another NULL
deref in fifo_set_limit() [1] I could repro the issue with : unshare -n tc
qd add dev lo root handle 1:0 tbf limit 200000 burst 70000 rate 100Mbit tc
qd replace dev lo parent 1:0 pfifo_fast tc qd change dev lo root handle 1:0
tbf limit 300000 burst 70000 rate 100Mbit pfifo_fast does not have a
change() operation. Make fifo_set_limit() more robust about this. [1] BUG:
kernel NULL pointer dereference, address: 0000000000000000 PGD 1cf99067 P4D
1cf99067 PUD 7ca49067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN CPU: 1 PID:
14443 Comm: syz-executor959 Not tainted 5.15.0-rc3-syzkaller #0 Hardware
name: Google Google Compute Engine/Google Compute Engine, BIOS Google
01/01/2011 RIP: 0010:0x0 Code: Unable to access opcode bytes at RIP
0xffffffffffffffd6. RSP: 0018:ffffc9000e2f7310 EFLAGS: 00010246 RAX:
dffffc0000000000 RBX: ffffffff8d6ecc00 RCX: 0000000000000000 RDX:
0000000000000000 RSI: ffff888024c27910 RDI: ffff888071e34000 RBP:
ffff888071e34000 R08: 0000000000000001 R09: ffffffff8fcfb947 R10:
0000000000000001 R11: 0000000000000000 R12: ffff888024c27910 R13:
ffff888071e34018 R14: 0000000000000000 R15: ffff88801ef74800 FS:
00007f321d897700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS:
0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3:
00000000722c3000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1:
0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6:
00000000fffe0ff0 DR7: 0000000000000400 Call Trace: fifo_set_limit
net/sched/sch_fifo.c:242 [inline] fifo_set_limit+0x198/0x210
net/sched/sch_fifo.c:227 tbf_change+0x6ec/0x16d0 net/sched/sch_tbf.c:418
qdisc_change net/sched/sch_api.c:1332 [inline] tc_modify_qdisc+0xd9a/0x1a60
net/sched/sch_api.c:1634 rtnetlink_rcv_msg+0x413/0xb80
net/core/rtnetlink.c:5572 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+0x86d/0xdb0
net/netlink/af_netlink.c:1929 sock_sendmsg_nosec net/socket.c:704 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:724 ____sys_sendmsg+0x6e8/0x810
net/socket.c:2409 ___sys_sendmsg+0xf3/0x170 net/socket.c:2463
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2492 do_syscall_x64
arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0
arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae