dm: fix mempool NULL pointer race when completing IO

Description

In the Linux kernel, the following vulnerability has been resolved: dm: fix mempool NULL pointer race when completing IO dm_io_dec_pending() calls end_io_acct() first and will then dec md in-flight pending count. But if a task is swapping DM table at same time this can result in a crash due to mempool->elements being NULL: task1 task2 do_resume ->do_suspend ->dm_wait_for_completion bio_endio ->clone_endio ->dm_io_dec_pending ->end_io_acct ->wakeup task1 ->dm_swap_table ->__bind ->__bind_mempools ->bioset_exit ->mempool_exit ->free_io [ 67.330330] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 ...... [ 67.330494] pstate: 80400085 (Nzcv daIf +PAN -UAO) [ 67.330510] pc : mempool_free+0x70/0xa0 [ 67.330515] lr : mempool_free+0x4c/0xa0 [ 67.330520] sp : ffffff8008013b20 [ 67.330524] x29: ffffff8008013b20 x28: 0000000000000004 [ 67.330530] x27: ffffffa8c2ff40a0 x26: 00000000ffff1cc8 [ 67.330535] x25: 0000000000000000 x24: ffffffdada34c800 [ 67.330541] x23: 0000000000000000 x22: ffffffdada34c800 [ 67.330547] x21: 00000000ffff1cc8 x20: ffffffd9a1304d80 [ 67.330552] x19: ffffffdada34c970 x18: 000000b312625d9c [ 67.330558] x17: 00000000002dcfbf x16: 00000000000006dd [ 67.330563] x15: 000000000093b41e x14: 0000000000000010 [ 67.330569] x13: 0000000000007f7a x12: 0000000034155555 [ 67.330574] x11: 0000000000000001 x10: 0000000000000001 [ 67.330579] x9 : 0000000000000000 x8 : 0000000000000000 [ 67.330585] x7 : 0000000000000000 x6 : ffffff80148b5c1a [ 67.330590] x5 : ffffff8008013ae0 x4 : 0000000000000001 [ 67.330596] x3 : ffffff80080139c8 x2 : ffffff801083bab8 [ 67.330601] x1 : 0000000000000000 x0 : ffffffdada34c970 [ 67.330609] Call trace: [ 67.330616] mempool_free+0x70/0xa0 [ 67.330627] bio_put+0xf8/0x110 [ 67.330638] dec_pending+0x13c/0x230 [ 67.330644] clone_endio+0x90/0x180 [ 67.330649] bio_endio+0x198/0x1b8 [ 67.330655] dec_pending+0x190/0x230 [ 67.330660] clone_endio+0x90/0x180 [ 67.330665] bio_endio+0x198/0x1b8 [ 67.330673] blk_update_request+0x214/0x428 [ 67.330683] scsi_end_request+0x2c/0x300 [ 67.330688] scsi_io_completion+0xa0/0x710 [ 67.330695] scsi_finish_command+0xd8/0x110 [ 67.330700] scsi_softirq_done+0x114/0x148 [ 67.330708] blk_done_softirq+0x74/0xd0 [ 67.330716] __do_softirq+0x18c/0x374 [ 67.330724] irq_exit+0xb4/0xb8 [ 67.330732] __handle_domain_irq+0x84/0xc0 [ 67.330737] gic_handle_irq+0x148/0x1b0 [ 67.330744] el1_irq+0xe8/0x190 [ 67.330753] lpm_cpuidle_enter+0x4f8/0x538 [ 67.330759] cpuidle_enter_state+0x1fc/0x398 [ 67.330764] cpuidle_enter+0x18/0x20 [ 67.330772] do_idle+0x1b4/0x290 [ 67.330778] cpu_startup_entry+0x20/0x28 [ 67.330786] secondary_start_kernel+0x160/0x170 Fix this by: 1) Establishing pointers to 'struct dm_io' members in dm_io_dec_pending() so that they may be passed into end_io_acct() _after_ free_io() is called. 2) Moving end_io_acct() after free_io().

Scores

EPSS (exploitation in 30 days)

0.24% · top 85% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.7.

Weakness

• CWE-476 (opens in a new tab)All about CWE-476 and its CVEs

Affected products

• Linux · Linux

  • affected 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 – < 9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed
  • affected 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 – < d35aef9c60d310eff3eaddacce301efe877e2b7c
  • affected 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 – < 9e07272cca2ed76f7f6073f4444b1143828c8d87
  • affected 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 – < ad1393b92e5059218d055bfec8f4946d85ad04c4
  • affected 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 – < d29c78d3f9c5d2604548c1065bf1ec212728ea61
  • affected 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 – < 6e506f07c5b561d673dd0b0d8f7f420cc48024fb
  • affected 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 – < d208b89401e073de986dc891037c5a668f5d5d95

• Linux · Linux

  • affected 2.6.37
  • unaffected < 2.6.37
  • unaffected 4.9.313 – ≤ 4.9.*
  • unaffected 4.14.278 – ≤ 4.14.*
  • unaffected 4.19.242 – ≤ 4.19.*
  • unaffected 5.4.193 – ≤ 5.4.*
  • unaffected 5.10.113 – ≤ 5.10.*
  • unaffected 5.14.14 – ≤ 5.14.*
  • unaffected 5.15 – ≤ *

References (7)

• https://git.kernel.org/stable/c/9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed (opens in a new tab)x_transferred
• https://git.kernel.org/stable/c/d35aef9c60d310eff3eaddacce301efe877e2b7c (opens in a new tab)x_transferred
• https://git.kernel.org/stable/c/9e07272cca2ed76f7f6073f4444b1143828c8d87 (opens in a new tab)x_transferred
• https://git.kernel.org/stable/c/ad1393b92e5059218d055bfec8f4946d85ad04c4 (opens in a new tab)x_transferred
• https://git.kernel.org/stable/c/d29c78d3f9c5d2604548c1065bf1ec212728ea61 (opens in a new tab)x_transferred
• https://git.kernel.org/stable/c/6e506f07c5b561d673dd0b0d8f7f420cc48024fb (opens in a new tab)x_transferred
• https://git.kernel.org/stable/c/d208b89401e073de986dc891037c5a668f5d5d95 (opens in a new tab)x_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2021-47435](https://trackcve.app/badge/CVE-2021-47435.svg)](https://trackcve.app/cve/CVE-2021-47435)

Record last updated 11 May 2026, 13:54 UTC.