{"id":"CVE-2026-74264","title":"net: watchdog: fix refcount tracking races","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: watchdog: fix refcount tracking races\n\nBlamed commit converted the untracked dev_hold()/dev_put() calls\nin the watchdog code to use the tracked dev_hold_track()/de…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= f12bf6f3f942b37de65eeea8be25903587fec930 < 446fe8ce699ce0a4d702f7b0fcdb50de340b9260","Linux >= f12bf6f3f942b37de65eeea8be25903587fec930 < 7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9","Linux >= f12bf6f3f942b37de65eeea8be25903587fec930 < 8eed5519e496b7a07f441a0f579cb228a33189f7","Linux 5.17"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T18:51:40.430593Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T18:55:28.702Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-74264","references":[{"url":"https://git.kernel.org/stable/c/446fe8ce699ce0a4d702f7b0fcdb50de340b9260"},{"url":"https://git.kernel.org/stable/c/7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9"},{"url":"https://git.kernel.org/stable/c/8eed5519e496b7a07f441a0f579cb228a33189f7"}],"tags":["cve.org"],"epss":0.00173,"epssPercentile":0.06315,"ingestedAt":"2026-10-16T19:46:24.387Z","slug":"CVE-2026-74264","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnet: watchdog: fix refcount tracking races\n\nBlamed commit converted the untracked dev_hold()/dev_put() calls\nin the watchdog code to use the tracked dev_hold_track()/dev_put_track()\n(which were later renamed/interfaced to netdev_hold() and netdev_put()).\n\nBy introducing dev->watchdog_dev_tracker to store the\nreference tracking information without adding synchronization\nbetween netdev_watchdog_up() and dev_watchdog(), it enabled the\nrace condition where this pointer could be overwritten or freed\nconcurrently, leading to the list corruption crash syzbot reported:\n\nlist_del corruption, ffff888114a18c00->next is NULL\n kernel BUG at lib/list_debug.c:52 !\nOops: invalid opcode: 0000 [#1] SMP KASAN PTI\nCPU: 1 UID: 0 PID: 91 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(lazy)\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026\nWorkqueue: events_unbound linkwatch_event\n RIP: 0010:__list_del_entry_valid_or_report.cold+0x22/0x2a lib/list_debug.c:52\nCall Trace:\n <TASK>\n  __list_del_entry_valid include/linux/list.h:132 [inline]\n  __list_del_entry include/linux/list.h:246 [inline]\n  list_move_tail include/linux/list.h:341 [inline]\n  ref_tracker_free+0x1a7/0x6c0 lib/ref_tracker.c:329\n  netdev_tracker_free include/linux/netdevice.h:4491 [inline]\n  netdev_put include/linux/netdevice.h:4508 [inline]\n  netdev_put include/linux/netdevice.h:4504 [inline]\n  netdev_watchdog_down net/sched/sch_generic.c:600 [inline]\n  dev_deactivate_many+0x28c/0xfe0 net/sched/sch_generic.c:1363\n  dev_deactivate+0x109/0x1d0 net/sched/sch_generic.c:1397\n  linkwatch_do_dev net/core/link_watch.c:184 [inline]\n  linkwatch_do_dev+0xd3/0x120 net/core/link_watch.c:166\n  __linkwatch_run_queue+0x3a5/0x810 net/core/link_watch.c:240\n  linkwatch_event+0x8f/0xc0 net/core/link_watch.c:314\n  process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314\n  process_scheduled_works kernel/workqueue.c:3397 [inline]\n  worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478\n  kthread+0x370/0x450 kernel/kthread.c:436\n  ret_from_fork+0x69a/0xc80 arch/x86/kernel/process.c:158\n  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245\n\nThis patch has three coordinated parts:\n\n1) Add dev->watchdog_lock and dev->watchdog_ref_held to serialize watchdog operations.\n\n2) Remove netdev_watchdog_up() call from netif_carrier_on():\n   This ensures netdev_watchdog_up() is only called from process/BH context\n   (via linkwatch workqueue dev_activate()), allowing us to use\n   spin_lock_bh() for synchronization.\n\n3) Synchronize watchdog up and watchdog timer:\n   Protect netdev_watchdog_up() with tx_global_lock and watchdog_lock.\n   Only allocate a new tracker in netdev_watchdog_up() if one is\n   not already present.\n   In dev_watchdog(), ensure we don't release the tracker if the\n   timer was rescheduled either by dev_watchdog() itself or concurrently\n   by netdev_watchdog_up().\n\n## Affected\n\n- `Linux >= f12bf6f3f942b37de65eeea8be25903587fec930 < 446fe8ce699ce0a4d702f7b0fcdb50de340b9260`\n- `Linux >= f12bf6f3f942b37de65eeea8be25903587fec930 < 7ce2b00ff058ec4cafc9b447e1f0a6d6f49275d9`\n- `Linux >= f12bf6f3f942b37de65eeea8be25903587fec930 < 8eed5519e496b7a07f441a0f579cb228a33189f7`\n- `Linux 5.17`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}