CVE-2026-93269: ext4: fix circular lock dependency in ext4_ext_migrate

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-24 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix circular lock dependency in ext4_ext_migrate Move iput(tmp_inode) after ext4_writepages_up_write() to avoid a circular lock dependency between s_writepages_rwsem and sb_internal (freeze protection). The deadlock scenario: CPU0 (EXT4_IOC_MIGRATE) CPU1 (orphan cleanup during mount) ---- ---- ext4_ext_migrate() ext4_writepages_down_write() s_writepages_rwsem (write) ext4_evict_inode() sb_start_intwrite() [sb_internal] ... ext4_writepages() s_writepages_rwsem (read) [BLOCKED] iput(tmp_inode) ext4_evict_inode() sb_start_intwrite() [BLOCKED] The tmp_inode is a temporary inode with nlink=0 created solely for building the extent tree. Its eviction does not require s_writepages_rwsem protection, so deferring iput() until after releasing the rwsem is safe.

Affected products

Linux: from 4.9.215 before 4.10; from 4.14.172 before 4.15; from 4.19.107 before 4.20; from 5.4.23 before 5.5; from 5.5.7 before 5.6 — fixed in 4.10, 4.15, 4.20, 5.5, 5.6

How to fix

Upgrade to a fixed version: Linux 4.10, 4.15, 4.20, 5.5. Check the vendor advisory for mitigations.

References

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