CVE-2023-53149: ext4: avoid deadlock in fs reclaim with page writeback

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-09-15 · updated 2026-10-30
Weakness: CWE-667

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: avoid deadlock in fs reclaim with page writeback Ext4 has a filesystem wide lock protecting ext4_writepages() calls to avoid races with switching of journalled data flag or inode format. This lock can however cause a deadlock like: CPU0 CPU1 ext4_writepages() percpu_down_read(sbi->s_writepages_rwsem); ext4_change_inode_journal_flag() percpu_down_write(sbi->s_writepages_rwsem); - blocks, all readers block from now on ext4_do_writepages() ext4_init_io_end() kmem_cache_zalloc(io_end_cachep, GFP_KERNEL) fs_reclaim frees dentry... dentry_unlink_inode() iput() - last ref => iput_final() - inode dirty => write_inode_now()... ext4_writepages() tries to acquire sbi->s_writepages_rwsem and blocks forever Make sure we cannot recurse into filesystem reclaim from writeback code to avoid the deadlock.

Affected products

Linux kernel: from 4.7 before 6.2.16; from 6.3 before 6.3.3; 6.4-rc1 — fixed in 6.2.16, 6.3.3
Linux: 4.7 — fixed in 6.4

How to fix

Upgrade to a fixed version: Linux kernel 6.2.16, 6.3.3; Linux 6.4. Check the vendor advisory for mitigations.

References

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