{"id":"CVE-2021-47418","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: fix NULL deref in fifo_set_limit()\n\nsyzbot reported another NULL deref in fifo_set_limit() [1]\n\nI could repro the issue with :\n\nunshare -n\ntc qd add dev lo root handle 1:0 tbf limit 200000 burst 70000 rate 100Mbit\ntc qd replace dev lo parent 1:0 pfifo_fast\ntc qd change dev lo root handle 1:0 tbf limit 300000 burst 70000 rate 100Mbit\n\npfifo_fast does not have a change() operation.\nMake fifo_set_limit() more robust about this.\n\n[1]\nBUG: kernel NULL pointer dereference, address: 0000000000000000\nPGD 1cf99067 P4D 1cf99067 PUD 7ca49067 PMD 0\nOops: 0010 [#1] PREEMPT SMP KASAN\nCPU: 1 PID: 14443 Comm: syz-executor959 Not tainted 5.15.0-rc3-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\nRIP: 0010:0x0\nCode: Unable to access opcode bytes at RIP 0xffffffffffffffd6.\nRSP: 0018:ffffc9000e2f7310 EFLAGS: 00010246\nRAX: dffffc0000000000 RBX: ffffffff8d6ecc00 RCX: 0000000000000000\nRDX: 0000000000000000 RSI: ffff888024c27910 RDI: ffff888071e34000\nRBP: ffff888071e34000 R08: 0000000000000001 R09: ffffffff8fcfb947\nR10: 0000000000000001 R11: 0000000000000000 R12: ffff888024c27910\nR13: ffff888071e34018 R14: 0000000000000000 R15: ffff88801ef74800\nFS:  00007f321d897700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: ffffffffffffffd6 CR3: 00000000722c3000 CR4: 00000000003506e0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n fifo_set_limit net/sched/sch_fifo.c:242 [inline]\n fifo_set_limit+0x198/0x210 net/sched/sch_fifo.c:227\n tbf_change+0x6ec/0x16d0 net/sched/sch_tbf.c:418\n qdisc_change net/sched/sch_api.c:1332 [inline]\n tc_modify_qdisc+0xd9a/0x1a60 net/sched/sch_api.c:1634\n rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5572\n netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504\n netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]\n netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340\n netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929\n sock_sendmsg_nosec net/socket.c:704 [inline]\n sock_sendmsg+0xcf/0x120 net/socket.c:724\n ____sys_sendmsg+0x6e8/0x810 net/socket.c:2409\n ___sys_sendmsg+0xf3/0x170 net/socket.c:2463\n __sys_sendmsg+0xe5/0x1b0 net/socket.c:2492\n do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80\n entry_SYSCALL_64_after_hwframe+0x44/0xae","modified":"2026-03-15T14:45:49.156534Z","published":"2024-05-21T15:15:27.257Z","related":["SUSE-SU-2024:2008-1","SUSE-SU-2024:2011-1","SUSE-SU-2024:2019-1","SUSE-SU-2024:2189-1","SUSE-SU-2024:2190-1","SUSE-SU-2024:2360-1","SUSE-SU-2024:2381-1","SUSE-SU-2024:2561-1"],"references":[{"type":"FIX","url":"https://git.kernel.org/stable/c/fb58cd7991747b5e0b110c98c922d7b0e47a1f14"},{"type":"FIX","url":"https://git.kernel.org/stable/c/08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4"},{"type":"FIX","url":"https://git.kernel.org/stable/c/0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52"},{"type":"FIX","url":"https://git.kernel.org/stable/c/26af64d71b6277841285fa40e3f7164a378dfda9"},{"type":"FIX","url":"https://git.kernel.org/stable/c/560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc"},{"type":"FIX","url":"https://git.kernel.org/stable/c/acff2d182c0768a713cee77442caeb07668bd68f"},{"type":"FIX","url":"https://git.kernel.org/stable/c/c951a3be5e8803e93bb49a0aca0d30457d3c1b67"},{"type":"FIX","url":"https://git.kernel.org/stable/c/d07098f45be868a9cdce6c616563c36c64dbbd87"}],"affected":[{"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-47418.json","unresolved_ranges":[{"events":[{"introduced":"2.6.27"},{"fixed":"4.4.289"}]},{"events":[{"introduced":"4.5"},{"fixed":"4.9.287"}]},{"events":[{"introduced":"4.10"},{"fixed":"4.14.251"}]},{"events":[{"introduced":"4.15"},{"fixed":"4.19.211"}]},{"events":[{"introduced":"4.20"},{"fixed":"5.4.153"}]},{"events":[{"introduced":"5.5"},{"fixed":"5.10.73"}]},{"events":[{"introduced":"5.11"},{"fixed":"5.14.12"}]},{"events":[{"introduced":"0"},{"last_affected":"5.15-rc1"}]},{"events":[{"introduced":"0"},{"last_affected":"5.15-rc2"}]},{"events":[{"introduced":"0"},{"last_affected":"5.15-rc3"}]},{"events":[{"introduced":"0"},{"last_affected":"5.15-rc4"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}