CVE-2022-49970
Analyzed Analyzed - Analysis Complete
BaseFortify

Publication date: 2025-06-18

Last updated on: 2026-01-23

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: bpf, cgroup: Fix kernel BUG in purge_effective_progs Syzkaller reported a triggered kernel BUG as follows: ------------[ cut here ]------------ kernel BUG at kernel/bpf/cgroup.c:925! invalid opcode: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 PID: 194 Comm: detach Not tainted 5.19.0-14184-g69dac8e431af #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 RIP: 0010:__cgroup_bpf_detach+0x1f2/0x2a0 Code: 00 e8 92 60 30 00 84 c0 75 d8 4c 89 e0 31 f6 85 f6 74 19 42 f6 84 28 48 05 00 00 02 75 0e 48 8b 80 c0 00 00 00 48 85 c0 75 e5 <0f> 0b 48 8b 0c5 RSP: 0018:ffffc9000055bdb0 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff888100ec0800 RCX: ffffc900000f1000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff888100ec4578 RBP: 0000000000000000 R08: ffff888100ec0800 R09: 0000000000000040 R10: 0000000000000000 R11: 0000000000000000 R12: ffff888100ec4000 R13: 000000000000000d R14: ffffc90000199000 R15: ffff888100effb00 FS: 00007f68213d2b80(0000) GS:ffff88813bc80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055f74a0e5850 CR3: 0000000102836000 CR4: 00000000000006e0 Call Trace: <TASK> cgroup_bpf_prog_detach+0xcc/0x100 __sys_bpf+0x2273/0x2a00 __x64_sys_bpf+0x17/0x20 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f68214dbcb9 Code: 08 44 89 e0 5b 41 5c c3 66 0f 1f 84 00 00 00 00 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 ff8 RSP: 002b:00007ffeb487db68 EFLAGS: 00000246 ORIG_RAX: 0000000000000141 RAX: ffffffffffffffda RBX: 000000000000000b RCX: 00007f68214dbcb9 RDX: 0000000000000090 RSI: 00007ffeb487db70 RDI: 0000000000000009 RBP: 0000000000000003 R08: 0000000000000012 R09: 0000000b00000003 R10: 00007ffeb487db70 R11: 0000000000000246 R12: 00007ffeb487dc20 R13: 0000000000000004 R14: 0000000000000001 R15: 000055f74a1011b0 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- Repetition steps: For the following cgroup tree, root | cg1 | cg2 1. attach prog2 to cg2, and then attach prog1 to cg1, both bpf progs attach type is NONE or OVERRIDE. 2. write 1 to /proc/thread-self/fail-nth for failslab. 3. detach prog1 for cg1, and then kernel BUG occur. Failslab injection will cause kmalloc fail and fall back to purge_effective_progs. The problem is that cg2 have attached another prog, so when go through cg2 layer, iteration will add pos to 1, and subsequent operations will be skipped by the following condition, and cg will meet NULL in the end. `if (pos && !(cg->bpf.flags[atype] & BPF_F_ALLOW_MULTI))` The NULL cg means no link or prog match, this is as expected, and it's not a bug. So here just skip the no match situation.
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Meta Information
Published
2025-06-18
Last Modified
2026-01-23
Generated
2026-05-07
AI Q&A
2025-06-18
EPSS Evaluated
2026-05-05
NVD
CVE-2022-49970
Affected Vendors & Products
Showing 7 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 5.10.138 (inc) to 5.10.142 (exc)
linux linux_kernel From 5.15.61 (inc) to 5.15.66 (exc)
linux linux_kernel From 5.18.18 (inc) to 5.19 (exc)
linux linux_kernel From 5.19.2 (inc) to 5.19.8 (exc)
linux linux_kernel 6.0
linux linux_kernel 6.0
linux linux_kernel 6.0
Helpful Resources
Exploitability
CWE
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CWE ID Description
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a kernel BUG in the Linux kernel's BPF cgroup code, specifically in the purge_effective_progs function. It occurs when detaching BPF programs from cgroups under certain conditions involving multiple attached programs and memory allocation failures (kmalloc fail). The bug leads to a NULL pointer dereference due to incorrect handling of program iteration and flags, causing the kernel to crash.


How can this vulnerability impact me? :

This vulnerability can cause the Linux kernel to crash (kernel BUG) when detaching BPF programs from cgroups under specific conditions. Such crashes can lead to system instability, denial of service, and potential disruption of services running on affected systems.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability manifests as a kernel BUG triggered during detaching BPF programs from cgroups, which can be detected by monitoring kernel logs for messages similar to 'kernel BUG at kernel/bpf/cgroup.c:925!' or related stack traces involving __cgroup_bpf_detach. You can check kernel logs using commands like 'dmesg | grep -i "kernel BUG"' or 'journalctl -k | grep -i "cgroup_bpf_detach"'. Additionally, monitoring for crashes or oops messages related to BPF and cgroup operations can help detect this issue.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where this vulnerability is fixed, as the issue is resolved in the kernel code. Avoid detaching BPF programs from cgroups in the specific sequence that triggers the bug, especially when using fail-nth for failslab injection or similar testing. If updating is not immediately possible, restrict or monitor operations that attach or detach BPF programs to cgroups to prevent triggering the kernel BUG.


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