{"cve":"CVE-2026-31703","nvd":{"published":"2026-05-01T14:16:20.263","modified":"2026-07-24T15:17:15.810","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nwriteback: Fix use after free in inode_switch_wbs_work_fn()\n\ninode_switch_wbs_work_fn() has a loop like:\n\n  wb_get(new_wb);\n  while (1) {\n    list = llist_del_all(&new_wb->switch_wbs_ctxs);\n    /* Nothing to do? */\n    if (!list)\n      break;\n    ... process the items ...\n  }\n\nNow adding of items to the list looks like:\n\nwb_queue_isw()\n  if (llist_add(&isw->list, &wb->switch_wbs_ctxs))\n    queue_work(isw_wq, &wb->switch_work);\n\nBecause inode_switch_wbs_work_fn() loops when processing isw items, it\ncan happen that wb->switch_work is pending while wb->switch_wbs_ctxs is\nempty. This is a problem because in that case wb can get freed (no isw\nitems -> no wb reference) while the work is still pending causing\nuse-after-free issues.\n\nWe cannot just fix this by cancelling work when freeing wb because that\ncould still trigger problematic 0 -> 1 transitions on wb refcount due to\nwb_get() in inode_switch_wbs_work_fn(). It could be all handled with\nmore careful code but that seems unnecessarily complex so let's avoid\nthat until it is proven that the looping actually brings practical\nbenefit. Just remove the loop from inode_switch_wbs_work_fn() instead.\nThat way when wb_queue_isw() queues work, we are guaranteed we have\nadded the first item to wb->switch_wbs_ctxs and nobody is going to\nremove it (and drop the wb reference it holds) until the queued work\nruns.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-416","CWE-825"],"references":["https://git.kernel.org/stable/c/028103656b84273c73e9e271cf95c9f3421f4b8a","https://git.kernel.org/stable/c/156cc63691c1f20905510b1007896e090355e6c2","https://git.kernel.org/stable/c/19ec404b079be057b387643ba0c69bbcc5867c35","https://git.kernel.org/stable/c/382cf81cae89e58d22b4bdc38891cd4d0b9ba921","https://git.kernel.org/stable/c/6689f01d6740cf358932b3e97ee968c6099800d9"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:33:09.003606135+00:00"},"epss":{"cve":"CVE-2026-31703","score":0.00119,"percentile":0.0174,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}