CVE-2021-47418: net_sched: fix NULL deref in fifo_set_limit()
First published: Tue May 21 2024(Updated: )
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
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | >=2.6.27<4.4.289 | |
| Linux Kernel | >=4.5<4.9.287 | |
| Linux Kernel | >=4.10<4.14.251 | |
| Linux Kernel | >=4.15<4.19.211 | |
| Linux Kernel | >=4.20<5.4.153 | |
| Linux Kernel | >=5.5<5.10.73 | |
| Linux Kernel | >=5.11<5.14.12 | |
| Linux Kernel | =5.15-rc1 | |
| Linux Kernel | =5.15-rc2 | |
| Linux Kernel | =5.15-rc3 | |
| Linux Kernel | =5.15-rc4 |
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Reference Links
- https://git.kernel.org/stable/c/0dd7ddc462b9c2d31eb5a9926a2cc63eaa3e9f52
- https://git.kernel.org/stable/c/08d7056e8e250fd2e67dbea5be5fdecdd75bf6b4
- https://git.kernel.org/stable/c/26af64d71b6277841285fa40e3f7164a378dfda9
- https://git.kernel.org/stable/c/d07098f45be868a9cdce6c616563c36c64dbbd87
- https://git.kernel.org/stable/c/c951a3be5e8803e93bb49a0aca0d30457d3c1b67
- https://git.kernel.org/stable/c/acff2d182c0768a713cee77442caeb07668bd68f
- https://git.kernel.org/stable/c/fb58cd7991747b5e0b110c98c922d7b0e47a1f14
- https://git.kernel.org/stable/c/560ee196fe9e5037e5015e2cdb14b3aecb1cd7dc
Frequently Asked Questions
What is the severity of CVE-2021-47418?
CVE-2021-47418 has been classified as a medium severity vulnerability in the Linux kernel.
How do I fix CVE-2021-47418?
To fix CVE-2021-47418, you should update your Linux kernel to the latest patched version that addresses this vulnerability.
What versions of the Linux kernel are affected by CVE-2021-47418?
CVE-2021-47418 affects multiple versions of the Linux kernel, specifically between 2.6.27 and 5.15-rc4.
What types of attacks can exploit CVE-2021-47418?
CVE-2021-47418 can potentially be exploited to cause a denial of service by triggering a NULL dereference in the kernel.
Is a system restart required after applying the patch for CVE-2021-47418?
Yes, a system restart is typically required to fully apply the kernel patch for CVE-2021-47418.
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