{"id":"AZL-74426","summary":"CVE-2025-68815 affecting package kernel for versions less than 6.6.121.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: ets: Remove drr class from the active list if it changes to strict\n\nWhenever a user issues an ets qdisc change command, transforming a\ndrr class into a strict one, the ets code isn't checking whether that\nclass was in the active list and removing it. This means that, if a\nuser changes a strict class (which was in the active list) back to a drr\none, that class will be added twice to the active list [1].\n\nDoing so with the following commands:\n\ntc qdisc add dev lo root handle 1: ets bands 2 strict 1\ntc qdisc add dev lo parent 1:2 handle 20: \\\n    tbf rate 8bit burst 100b latency 1s\ntc filter add dev lo parent 1: basic classid 1:2\nping -c1 -W0.01 -s 56 127.0.0.1\ntc qdisc change dev lo root handle 1: ets bands 2 strict 2\ntc qdisc change dev lo root handle 1: ets bands 2 strict 1\nping -c1 -W0.01 -s 56 127.0.0.1\n\nWill trigger the following splat with list debug turned on:\n\n[   59.279014][  T365] ------------[ cut here ]------------\n[   59.279452][  T365] list_add double add: new=ffff88801d60e350, prev=ffff88801d60e350, next=ffff88801d60e2c0.\n[   59.280153][  T365] WARNING: CPU: 3 PID: 365 at lib/list_debug.c:35 __list_add_valid_or_report+0x17f/0x220\n[   59.280860][  T365] Modules linked in:\n[   59.281165][  T365] CPU: 3 UID: 0 PID: 365 Comm: tc Not tainted 6.18.0-rc7-00105-g7e9f13163c13-dirty #239 PREEMPT(voluntary)\n[   59.281977][  T365] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011\n[   59.282391][  T365] RIP: 0010:__list_add_valid_or_report+0x17f/0x220\n[   59.282842][  T365] Code: 89 c6 e8 d4 b7 0d ff 90 0f 0b 90 90 31 c0 e9 31 ff ff ff 90 48 c7 c7 e0 a0 22 9f 48 89 f2 48 89 c1 4c 89 c6 e8 b2 b7 0d ff 90 \u003c0f\u003e 0b 90 90 31 c0 e9 0f ff ff ff 48 89 f7 48 89 44 24 10 4c 89 44\n...\n[   59.288812][  T365] Call Trace:\n[   59.289056][  T365]  \u003cTASK\u003e\n[   59.289224][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   59.289546][  T365]  ets_qdisc_change+0xd2b/0x1e80\n[   59.289891][  T365]  ? __lock_acquire+0x7e7/0x1be0\n[   59.290223][  T365]  ? __pfx_ets_qdisc_change+0x10/0x10\n[   59.290546][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   59.290898][  T365]  ? __mutex_trylock_common+0xda/0x240\n[   59.291228][  T365]  ? __pfx___mutex_trylock_common+0x10/0x10\n[   59.291655][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   59.291993][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   59.292313][  T365]  ? trace_contention_end+0xc8/0x110\n[   59.292656][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   59.293022][  T365]  ? srso_alias_return_thunk+0x5/0xfbef5\n[   59.293351][  T365]  tc_modify_qdisc+0x63a/0x1cf0\n\nFix this by always checking and removing an ets class from the active list\nwhen changing it to strict.\n\n[1] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/tree/net/sched/sch_ets.c?id=ce052b9402e461a9aded599f5b47e76bc727f7de#n663","modified":"2026-04-01T05:22:43.677031Z","published":"2026-01-13T16:16:03Z","upstream":["CVE-2025-68815"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-68815"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.121.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-74426.json"}}],"schema_version":"1.7.5"}