{"cve":"CVE-2021-47492","nvd":{"published":"2024-05-22T09:15:11.030","modified":"2026-08-04T10:17:05.447","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm, thp: bail out early in collapse_file for writeback page\n\nCurrently collapse_file does not explicitly check PG_writeback, instead,\npage_has_private and try_to_release_page are used to filter writeback\npages.  This does not work for xfs with blocksize equal to or larger\nthan pagesize, because in such case xfs has no page->private.\n\nThis makes collapse_file bail out early for writeback page.  Otherwise,\nxfs end_page_writeback will panic as follows.\n\n  page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:ffff0003f88c86a8 index:0x0 pfn:0x84ef32\n  aops:xfs_address_space_operations [xfs] ino:30000b7 dentry name:\"libtest.so\"\n  flags: 0x57fffe0000008027(locked|referenced|uptodate|active|writeback)\n  raw: 57fffe0000008027 ffff80001b48bc28 ffff80001b48bc28 ffff0003f88c86a8\n  raw: 0000000000000000 0000000000000000 00000000ffffffff ffff0000c3e9a000\n  page dumped because: VM_BUG_ON_PAGE(((unsigned int) page_ref_count(page) + 127u <= 127u))\n  page->mem_cgroup:ffff0000c3e9a000\n  ------------[ cut here ]------------\n  kernel BUG at include/linux/mm.h:1212!\n  Internal error: Oops - BUG: 0 [#1] SMP\n  Modules linked in:\n  BUG: Bad page state in process khugepaged  pfn:84ef32\n   xfs(E)\n  page:fffffe00201bcc80 refcount:0 mapcount:0 mapping:0 index:0x0 pfn:0x84ef32\n   libcrc32c(E) rfkill(E) aes_ce_blk(E) crypto_simd(E) ...\n  CPU: 25 PID: 0 Comm: swapper/25 Kdump: loaded Tainted: ...\n  pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--)\n  Call trace:\n    end_page_writeback+0x1c0/0x214\n    iomap_finish_page_writeback+0x13c/0x204\n    iomap_finish_ioend+0xe8/0x19c\n    iomap_writepage_end_bio+0x38/0x50\n    bio_endio+0x168/0x1ec\n    blk_update_request+0x278/0x3f0\n    blk_mq_end_request+0x34/0x15c\n    virtblk_request_done+0x38/0x74 [virtio_blk]\n    blk_done_softirq+0xc4/0x110\n    __do_softirq+0x128/0x38c\n    __irq_exit_rcu+0x118/0x150\n    irq_exit+0x1c/0x30\n    __handle_domain_irq+0x8c/0xf0\n    gic_handle_irq+0x84/0x108\n    el1_irq+0xcc/0x180\n    arch_cpu_idle+0x18/0x40\n    default_idle_call+0x4c/0x1a0\n    cpuidle_idle_call+0x168/0x1e0\n    do_idle+0xb4/0x104\n    cpu_startup_entry+0x30/0x9c\n    secondary_start_kernel+0x104/0x180\n  Code: d4210000 b0006161 910c8021 94013f4d (d4210000)\n  ---[ end trace 4a88c6a074082f8c ]---\n  Kernel panic - not syncing: Oops - BUG: Fatal exception in interrupt","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/5e669d8ab30ab61dec3c36e27b4711f07611e6fc","https://git.kernel.org/stable/c/69a7fa5cb0de06c8956b040f19a7248c8c8308ca","https://git.kernel.org/stable/c/74c42e1baacf206338b1dd6b6199ac964512b5bb","https://git.kernel.org/stable/c/5e669d8ab30ab61dec3c36e27b4711f07611e6fc","https://git.kernel.org/stable/c/69a7fa5cb0de06c8956b040f19a7248c8c8308ca"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:50:30.954589733+00:00"},"epss":{"cve":"CVE-2021-47492","score":0.00218,"percentile":0.12313,"date":"2026-11-01"},"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."]}