{"uuid": "09f0677a-04a4-46c7-97b6-2b548ce6501b", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "2a075640-a300-48a4-bb44-bc6130783b9b", "vulnerability": "CVE-2025-21643", "type": "published-proof-of-concept", "source": "https://t.me/DarkWebInformer_CVEAlerts/2323", "content": "\ud83d\udd17 DarkWebInformer.com - Cyber Threat Intelligence\n\ud83d\udccc CVE ID: CVE-2025-21643\n\ud83d\udd39 Description: In the Linux kernel, the following vulnerability has been resolved:\n\nnetfs: Fix kernel async DIO\n\nNetfslib needs to be able to handle kernel-initiated asynchronous DIO that\nis supplied with a bio_vec[] array.  Currently, because of the async flag,\nthis gets passed to netfs_extract_user_iter() which throws a warning and\nfails because it only handles IOVEC and UBUF iterators.  This can be\ntriggered through a combination of cifs and a loopback blockdev with\nsomething like:\n\n        mount //my/cifs/share /foo\n        dd if=/dev/zero of=/foo/m0 bs=4K count=1K\n        losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0\n        echo hello >/dev/loop2046\n\nThis causes the following to appear in syslog:\n\n        WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs]\n\nand the write to fail.\n\nFix this by removing the check in netfs_unbuffered_write_iter_locked() that\ncauses async kernel DIO writes to be handled as userspace writes.  Note\nthat this change relies on the kernel caller maintaining the existence of\nthe bio_vec array (or kvec[] or folio_queue) until the op is complete.\n\ud83d\udccf Published: 2025-01-19T10:17:59.820Z\n\ud83d\udccf Modified: 2025-01-19T10:17:59.820Z\n\ud83d\udd17 References:\n1. https://git.kernel.org/stable/c/9f3a265836844eda30bf34c2584b8011fd4f0f49\n2. https://git.kernel.org/stable/c/3f6bc9e3ab9b127171d39f9ac6eca1abb693b731", "creation_timestamp": "2025-01-19T10:58:27.000000Z"}