{"cve":"CVE-2021-47256","nvd":{"published":"2024-05-21T15:15:14.380","modified":"2026-06-17T04:17:01.693","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/memory-failure: make sure wait for page writeback in memory_failure\n\nOur syzkaller trigger the \"BUG_ON(!list_empty(&inode->i_wb_list))\" in\nclear_inode:\n\n  kernel BUG at fs/inode.c:519!\n  Internal error: Oops - BUG: 0 [#1] SMP\n  Modules linked in:\n  Process syz-executor.0 (pid: 249, stack limit = 0x00000000a12409d7)\n  CPU: 1 PID: 249 Comm: syz-executor.0 Not tainted 4.19.95\n  Hardware name: linux,dummy-virt (DT)\n  pstate: 80000005 (Nzcv daif -PAN -UAO)\n  pc : clear_inode+0x280/0x2a8\n  lr : clear_inode+0x280/0x2a8\n  Call trace:\n    clear_inode+0x280/0x2a8\n    ext4_clear_inode+0x38/0xe8\n    ext4_free_inode+0x130/0xc68\n    ext4_evict_inode+0xb20/0xcb8\n    evict+0x1a8/0x3c0\n    iput+0x344/0x460\n    do_unlinkat+0x260/0x410\n    __arm64_sys_unlinkat+0x6c/0xc0\n    el0_svc_common+0xdc/0x3b0\n    el0_svc_handler+0xf8/0x160\n    el0_svc+0x10/0x218\n  Kernel panic - not syncing: Fatal exception\n\nA crash dump of this problem show that someone called __munlock_pagevec\nto clear page LRU without lock_page: do_mmap -> mmap_region -> do_munmap\n-> munlock_vma_pages_range -> __munlock_pagevec.\n\nAs a result memory_failure will call identify_page_state without\nwait_on_page_writeback.  And after truncate_error_page clear the mapping\nof this page.  end_page_writeback won't call sb_clear_inode_writeback to\nclear inode->i_wb_list.  That will trigger BUG_ON in clear_inode!\n\nFix it by checking PageWriteback too to help determine should we skip\nwait_on_page_writeback.","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/28788dc5c70597395b6b451dae4549bbaa8e2c56","https://git.kernel.org/stable/c/566345aaabac853aa866f53a219c4b02a6beb527","https://git.kernel.org/stable/c/6d210d547adc2218ef8b5bcf23518c5f2f1fd872","https://git.kernel.org/stable/c/9e379da727a7a031be9b877cde7b9c34a0fb8306","https://git.kernel.org/stable/c/d05267fd27a5c4f54e06daefa3035995d765ca0c"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:50:30.954589733+00:00"},"epss":{"cve":"CVE-2021-47256","score":0.00233,"percentile":0.14249,"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."]}