CVE-2022-50000
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-06-18

Last updated on: 2025-11-14

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: flowtable: fix stuck flows on cleanup due to pending work To clear the flow table on flow table free, the following sequence normally happens in order: 1) gc_step work is stopped to disable any further stats/del requests. 2) All flow table entries are set to teardown state. 3) Run gc_step which will queue HW del work for each flow table entry. 4) Waiting for the above del work to finish (flush). 5) Run gc_step again, deleting all entries from the flow table. 6) Flow table is freed. But if a flow table entry already has pending HW stats or HW add work step 3 will not queue HW del work (it will be skipped), step 4 will wait for the pending add/stats to finish, and step 5 will queue HW del work which might execute after freeing of the flow table. To fix the above, this patch flushes the pending work, then it sets the teardown flag to all flows in the flowtable and it forces a garbage collector run to queue work to remove the flows from hardware, then it flushes this new pending work and (finally) it forces another garbage collector run to remove the entry from the software flowtable. Stack trace: [47773.882335] BUG: KASAN: use-after-free in down_read+0x99/0x460 [47773.883634] Write of size 8 at addr ffff888103b45aa8 by task kworker/u20:6/543704 [47773.885634] CPU: 3 PID: 543704 Comm: kworker/u20:6 Not tainted 5.12.0-rc7+ #2 [47773.886745] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009) [47773.888438] Workqueue: nf_ft_offload_del flow_offload_work_handler [nf_flow_table] [47773.889727] Call Trace: [47773.890214] dump_stack+0xbb/0x107 [47773.890818] print_address_description.constprop.0+0x18/0x140 [47773.892990] kasan_report.cold+0x7c/0xd8 [47773.894459] kasan_check_range+0x145/0x1a0 [47773.895174] down_read+0x99/0x460 [47773.899706] nf_flow_offload_tuple+0x24f/0x3c0 [nf_flow_table] [47773.907137] flow_offload_work_handler+0x72d/0xbe0 [nf_flow_table] [47773.913372] process_one_work+0x8ac/0x14e0 [47773.921325] [47773.921325] Allocated by task 592159: [47773.922031] kasan_save_stack+0x1b/0x40 [47773.922730] __kasan_kmalloc+0x7a/0x90 [47773.923411] tcf_ct_flow_table_get+0x3cb/0x1230 [act_ct] [47773.924363] tcf_ct_init+0x71c/0x1156 [act_ct] [47773.925207] tcf_action_init_1+0x45b/0x700 [47773.925987] tcf_action_init+0x453/0x6b0 [47773.926692] tcf_exts_validate+0x3d0/0x600 [47773.927419] fl_change+0x757/0x4a51 [cls_flower] [47773.928227] tc_new_tfilter+0x89a/0x2070 [47773.936652] [47773.936652] Freed by task 543704: [47773.937303] kasan_save_stack+0x1b/0x40 [47773.938039] kasan_set_track+0x1c/0x30 [47773.938731] kasan_set_free_info+0x20/0x30 [47773.939467] __kasan_slab_free+0xe7/0x120 [47773.940194] slab_free_freelist_hook+0x86/0x190 [47773.941038] kfree+0xce/0x3a0 [47773.941644] tcf_ct_flow_table_cleanup_work Original patch description and stack trace by Paul Blakey.
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Meta Information
Published
2025-06-18
Last Modified
2025-11-14
Generated
2026-05-07
AI Q&A
2025-06-18
EPSS Evaluated
2026-05-05
NVD
CVE-2022-50000
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
linux linux_kernel 6.0
linux linux_kernel 6.0
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability in the Linux kernel's netfilter flowtable occurs during the cleanup process of flow tables. Normally, a sequence of steps ensures that all flow table entries are properly removed and hardware work is completed before freeing the flow table. However, if a flow table entry has pending hardware stats or add work, the deletion work is skipped and may execute after the flow table is freed, causing a use-after-free bug. This can lead to kernel crashes or memory corruption. The fix involves flushing pending work and carefully sequencing the teardown and garbage collection to avoid this issue.


How can this vulnerability impact me? :

This vulnerability can cause use-after-free errors in the Linux kernel, potentially leading to system instability, crashes, or security issues such as privilege escalation or denial of service if exploited. It affects the reliability and security of systems using the affected kernel versions.


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

This vulnerability may be detected by monitoring kernel logs for use-after-free errors related to netfilter flowtable operations, such as KASAN (Kernel Address Sanitizer) reports showing stack traces involving nf_flow_table and flow_offload_work_handler. Commands like 'dmesg | grep -i kasan' or 'journalctl -k | grep nf_flow_table' can help identify such errors.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version that includes the patch fixing the flowtable cleanup issue. The patch ensures proper flushing of pending work and garbage collection to prevent use-after-free conditions. Until an update is applied, consider disabling or limiting netfilter flowtable offload features if possible to reduce exposure.


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