CVE-2024-26956: Debian Linux

High severity, CVSS 7.8. EPSS: 0.3% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix failure to detect DAT corruption in btree and direct mappings Patch series "nilfs2: fix kernel bug at submit_bh_wbc()". This resolves a kernel BUG reported by syzbot. Since there are two flaws involved, I've made each one a separate patch. The first patch alone resolves the syzbot-reported bug, but I think both fixes should be sent to stable, so I've tagged them as such. This patch (of 2): Syzbot has reported a kernel bug in submit_bh_wbc() when writing file data to a nilfs2 file system whose metadata is corrupted. There are two flaws involved in this issue. The first flaw is that when nilfs_get_block() locates a data block using btree or direct mapping, if the disk address translation routine nilfs_dat_translate() fails with internal code -ENOENT due to DAT metadata corruption, it can be passed back to nilfs_get_block(). This causes nilfs_get_block() to misidentify an existing block as non-existent, causing both data block lookup and insertion to fail inconsistently. The second flaw is that nilfs_get_block() returns a successful status in this inconsistent state. This causes the caller __block_write_begin_int() or others to request a read even though the buffer is not mapped, resulting in a BUG_ON check for the BH_Mapped flag in submit_bh_wbc() failing. This fixes the first issue by changing the return value to code -EINVAL when a conversion using DAT fails with code -ENOENT, avoiding the conflicting condition that leads to the kernel bug described above. Here, code -EINVAL indicates that metadata corruption was detected during the block lookup, which will be properly handled as a file system error and converted to -EIO when passing through the nilfs2 bmap layer.

Affected products

Debian Debian Linux: version 10.0 only
Linux Linux Kernel: from 2.6.31, before 4.19.312 (fixed in 4.19.312); from 4.20, before 5.4.274 (fixed in 5.4.274); from 5.5, before 5.10.215 (fixed in 5.10.215); from 5.11, before 5.15.154 (fixed in 5.15.154); from 5.16, before 6.1.84 (fixed in 6.1.84); from 6.2, before 6.6.24 (fixed in 6.6.24); …

Published 2024-05-01. Last modified 2026-06-17.