Linux x86 SYSENTER BHI Branch History Invalidation Vulnerability and Patch Analysis

From this webpage screenshot, we can extract the following key information about the vulnerability: 1. Vulnerability Description: - When the BHI (Branch History Invalidation) mechanism is enabled, if SYSENTER is invoked with the TF (Task Flag) bit set, the function will use and call , causing a #DB (Debug) exception to be triggered by the processor before the TF flag is cleared. 2. Reproduction Steps: - The issue can be reproduced by following these steps: 1. Write a program named containing the following code: 2. Compile the program using gcc. 3. Run the compiled program. - The expected result is a Segmentation fault (core dumped). 3. Solution: - The function should use only after ensuring that the TF flag has been cleared. 4. Patch Information: - This patch fixes the vulnerability introduced by commit 7390db8aea0d ("x86/bhi: Add support for clearing branch history at syscall entry"). - The patch was reported by Suman Maity, signed by Alexandre Chartre and Borislav Petkov (AMD), reviewed by Andrew Cooper and Pawan Gupta, and signed by Josh Poinboeuf and Sasha Levin. 5. Patch Content: - The patch is located in the file , primarily modifying the placement of the instruction. This information helps us understand the vulnerability's context, reproduction method, resolution, and associated patch details.

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Linux x86 SYSENTER BHI Branch History Invalidation Vulnerability and Patch Analysis