{"uuid": "0f147246-7a3c-4ecc-b349-c03dcd877bef", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "2a075640-a300-48a4-bb44-bc6130783b9b", "vulnerability": "CVE-2025-21897", "type": "published-proof-of-concept", "source": "https://t.me/DarkWebInformer_CVEAlerts/9923", "content": "\ud83d\udd17 DarkWebInformer.com - Cyber Threat Intelligence\n\ud83d\udccc CVE ID: CVE-2025-21897\n\ud83d\udd25 CVSS Score: N/A\n\ud83d\udd39 Description: In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Fix pick_task_scx() picking non-queued tasks when it's called without balance()\n\na6250aa251ea (\"sched_ext: Handle cases where pick_task_scx() is called\nwithout preceding balance_scx()\") added a workaround to handle the cases\nwhere pick_task_scx() is called without prececing balance_scx() which is due\nto a fair class bug where pick_taks_fair() may return NULL after a true\nreturn from balance_fair().\n\nThe workaround detects when pick_task_scx() is called without preceding\nbalance_scx() and emulates SCX_RQ_BAL_KEEP and triggers kicking to avoid\nstalling. Unfortunately, the workaround code was testing whether @prev was\non SCX to decide whether to keep the task running. This is incorrect as the\ntask may be on SCX but no longer runnable.\n\nThis could lead to a non-runnable task to be returned from pick_task_scx()\nwhich cause interesting confusions and failures. e.g. A common failure mode\nis the task ending up with (!on_rq && on_cpu) state which can cause\npotential wakers to busy loop, which can easily lead to deadlocks.\n\nFix it by testing whether @prev has SCX_TASK_QUEUED set. This makes\n@prev_on_scx only used in one place. Open code the usage and improve the\ncomment while at it.\n\ud83d\udccf Published: 2025-04-01T15:26:49.705Z\n\ud83d\udccf Modified: 2025-04-01T15:26:49.705Z\n\ud83d\udd17 References:\n1. https://git.kernel.org/stable/c/5324c459f90d16b0c43a78b494c598915d782b7a\n2. https://git.kernel.org/stable/c/de60a31cb0bcacfaf9487546eac5e70e0a9c66d7\n3. https://git.kernel.org/stable/c/8fef0a3b17bb258130a4fcbcb5addf94b25e9ec5", "creation_timestamp": "2025-04-01T15:32:40.000000Z"}