{"cve":"CVE-2021-47435","nvd":{"published":"2024-05-22T07:15:08.790","modified":"2026-06-17T04:17:27.853","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndm: fix mempool NULL pointer race when completing IO\n\ndm_io_dec_pending() calls end_io_acct() first and will then dec md\nin-flight pending count. But if a task is swapping DM table at same\ntime this can result in a crash due to mempool->elements being NULL:\n\ntask1                             task2\ndo_resume\n ->do_suspend\n  ->dm_wait_for_completion\n                                  bio_endio\n\t\t\t\t   ->clone_endio\n\t\t\t\t    ->dm_io_dec_pending\n\t\t\t\t     ->end_io_acct\n\t\t\t\t      ->wakeup task1\n ->dm_swap_table\n  ->__bind\n   ->__bind_mempools\n    ->bioset_exit\n     ->mempool_exit\n                                     ->free_io\n\n[ 67.330330] Unable to handle kernel NULL pointer dereference at\nvirtual address 0000000000000000\n......\n[ 67.330494] pstate: 80400085 (Nzcv daIf +PAN -UAO)\n[ 67.330510] pc : mempool_free+0x70/0xa0\n[ 67.330515] lr : mempool_free+0x4c/0xa0\n[ 67.330520] sp : ffffff8008013b20\n[ 67.330524] x29: ffffff8008013b20 x28: 0000000000000004\n[ 67.330530] x27: ffffffa8c2ff40a0 x26: 00000000ffff1cc8\n[ 67.330535] x25: 0000000000000000 x24: ffffffdada34c800\n[ 67.330541] x23: 0000000000000000 x22: ffffffdada34c800\n[ 67.330547] x21: 00000000ffff1cc8 x20: ffffffd9a1304d80\n[ 67.330552] x19: ffffffdada34c970 x18: 000000b312625d9c\n[ 67.330558] x17: 00000000002dcfbf x16: 00000000000006dd\n[ 67.330563] x15: 000000000093b41e x14: 0000000000000010\n[ 67.330569] x13: 0000000000007f7a x12: 0000000034155555\n[ 67.330574] x11: 0000000000000001 x10: 0000000000000001\n[ 67.330579] x9 : 0000000000000000 x8 : 0000000000000000\n[ 67.330585] x7 : 0000000000000000 x6 : ffffff80148b5c1a\n[ 67.330590] x5 : ffffff8008013ae0 x4 : 0000000000000001\n[ 67.330596] x3 : ffffff80080139c8 x2 : ffffff801083bab8\n[ 67.330601] x1 : 0000000000000000 x0 : ffffffdada34c970\n[ 67.330609] Call trace:\n[ 67.330616] mempool_free+0x70/0xa0\n[ 67.330627] bio_put+0xf8/0x110\n[ 67.330638] dec_pending+0x13c/0x230\n[ 67.330644] clone_endio+0x90/0x180\n[ 67.330649] bio_endio+0x198/0x1b8\n[ 67.330655] dec_pending+0x190/0x230\n[ 67.330660] clone_endio+0x90/0x180\n[ 67.330665] bio_endio+0x198/0x1b8\n[ 67.330673] blk_update_request+0x214/0x428\n[ 67.330683] scsi_end_request+0x2c/0x300\n[ 67.330688] scsi_io_completion+0xa0/0x710\n[ 67.330695] scsi_finish_command+0xd8/0x110\n[ 67.330700] scsi_softirq_done+0x114/0x148\n[ 67.330708] blk_done_softirq+0x74/0xd0\n[ 67.330716] __do_softirq+0x18c/0x374\n[ 67.330724] irq_exit+0xb4/0xb8\n[ 67.330732] __handle_domain_irq+0x84/0xc0\n[ 67.330737] gic_handle_irq+0x148/0x1b0\n[ 67.330744] el1_irq+0xe8/0x190\n[ 67.330753] lpm_cpuidle_enter+0x4f8/0x538\n[ 67.330759] cpuidle_enter_state+0x1fc/0x398\n[ 67.330764] cpuidle_enter+0x18/0x20\n[ 67.330772] do_idle+0x1b4/0x290\n[ 67.330778] cpu_startup_entry+0x20/0x28\n[ 67.330786] secondary_start_kernel+0x160/0x170\n\nFix this by:\n1) Establishing pointers to 'struct dm_io' members in\ndm_io_dec_pending() so that they may be passed into end_io_acct()\n_after_ free_io() is called.\n2) Moving end_io_acct() after free_io().","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H","score":4.7},"cwes":["CWE-476"],"references":["https://git.kernel.org/stable/c/6e506f07c5b561d673dd0b0d8f7f420cc48024fb","https://git.kernel.org/stable/c/9e07272cca2ed76f7f6073f4444b1143828c8d87","https://git.kernel.org/stable/c/9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed","https://git.kernel.org/stable/c/ad1393b92e5059218d055bfec8f4946d85ad04c4","https://git.kernel.org/stable/c/d208b89401e073de986dc891037c5a668f5d5d95"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:50:30.954589733+00:00"},"epss":{"cve":"CVE-2021-47435","score":0.00239,"percentile":0.14975,"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."]}