5.5

CVE-2021-47637: ubifs: Fix deadlock in concurrent rename whiteout and inode writeback

Modified
AliasesUBUNTU-CVE-2021-47637DEBIAN-CVE-2021-47637
Published 26-02-2025Last modified 11-05-2026

Vulnerability summary

CVE-2021-47637 is a medium (CVSS 5.5) Improper Locking vulnerability in linux. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 8.9% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.19%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 4 · Related 4
SUSE-SU-2025:1027-1SUSE-SU-2025:1176-1SUSE-SU-2025:1183-1SUSE-SU-2025:1241-1

Timeline

  1. 26-02-2025
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: ubifs: Fix deadlock in concurrent rename whiteout and inode writeback Following hung tasks: [ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132 [ 77.028820] Call Trace: [ 77.029027] schedule+0x8c/0x1b0 [ 77.029067] mutex_lock+0x50/0x60 [ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs] [ 77.029117] __writeback_single_inode+0x43c/0x570 [ 77.029128] writeback_sb_inodes+0x259/0x740 [ 77.029148] wb_writeback+0x107/0x4d0 [ 77.029163] wb_workfn+0x162/0x7b0 [ 92.390442] task:aa state:D stack: 0 pid: 1506 [ 92.390448] Call Trace: [ 92.390458] schedule+0x8c/0x1b0 [ 92.390461] wb_wait_for_completion+0x82/0xd0 [ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110 [ 92.390472] writeback_inodes_sb_nr+0x14/0x20 [ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs] [ 92.390503] do_rename.cold+0x7f/0x187 [ubifs] [ 92.390549] ubifs_rename+0x8b/0x180 [ubifs] [ 92.390571] vfs_rename+0xdb2/0x1170 [ 92.390580] do_renameat2+0x554/0x770 , are caused by concurrent rename whiteout and inode writeback processes: rename_whiteout(Thread 1) wb_workfn(Thread2) ubifs_rename do_rename lock_4_inodes (Hold ui_mutex) ubifs_budget_space make_free_space shrink_liability __writeback_inodes_sb_nr bdi_split_work_to_wbs (Queue new wb work) wb_do_writeback(wb work) __writeback_single_inode ubifs_write_inode LOCK(ui_mutex) ↑ wb_wait_for_completion (Wait wb work) <-- deadlock! Reproducer (Detail program in [Link]): 1. SYS_renameat2("/mp/dir/file", "/mp/dir/whiteout", RENAME_WHITEOUT) 2. Consume out of space before kernel(mdelay) doing budget for whiteout Fix it by doing whiteout space budget before locking ubifs inodes. BTW, it also fixes wrong goto tag 'out_release' in whiteout budget error handling path(It should at least recover dir i_size and unlock 4 ubifs inodes).

CVSS metrics

5 scores · 4 sources · 2 versions

EPSS trend

Probability

0.19%

Chance of exploitation in the next 30 days

Percentile

9%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.19% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu105 products
  • linux< 4.15.0-189.200 | < 5.4.0-117.132 | < 5.15.0-37.39
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws< 4.15.0-1137.148 | < 5.4.0-1078.84 | < 5.15.0-1011.14
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, < 9dddc8211430fb851ddf0b168e3a00c6f66cc185 | ≥ 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, < 37bdf1ad592555ecda1d55b89f6e393e4c0589d1 | ≥ 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, < 83e42a78428fc354f5e2049935b84c8d8d29b787 | ≥ 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, < c58af8564a7b08757173009030b74baf4b2b762b | ≥ 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, < 70e9090acc32348cedc5def0cd6d5c126efc97b9 | ≥ 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, < 8b278c8dcfb565cb65eceb62a38cbf7a7c326db5 | ≥ 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798, < afd427048047e8efdedab30e8888044e2be5aa9c | 4.9
  • linux_kernel≥ 4.9, < 4.19.238 | ≥ 4.20, < 5.4.189 | ≥ 5.5, < 5.10.110 | ≥ 5.11, < 5.15.33 | ≥ 5.16, < 5.16.19 | ≥ 5.17, < 5.17.2
Debian1 product
  • linux< 5.17.3-1

3 vendors · 108 products

References

11 links
Show all 11 references