tracing/user_events: Ensure write index cannot be negative

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: tracing/user_events: Ensure write index cannot be negative The write index indicates which event the data is for and accesses a per-file array. The index is passed by user processes during write() calls as the first 4 bytes. Ensure that it cannot be negative by returning -EINVAL to prevent out of bounds accesses. Update ftrace self-test to ensure this occurs properly.

References

• https://git.kernel.org/stable/c/0489c2b2c3104b89f078dbcec8c744dfc157d3e9
• https://git.kernel.org/stable/c/4fe46b5adf18e3dc606e62c9e6a0413398a17572
• https://git.kernel.org/stable/c/fa7f2f5d1739452280c22727c4384a52b72ab5de
• https://git.kernel.org/stable/c/cd98c93286a30cc4588dfd02453bec63c2f4acf4