CVE-2023-52874: x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
Description
In the Linux kernel, the following vulnerability has been resolved:
x86/tdx: Zero out the missing RSI in TDX_HYPERCALL macro
In the TDX_HYPERCALL asm, after the TDCALL instruction returns from the
untrusted VMM, the registers that the TDX guest shares to the VMM need
to be cleared to avoid speculative execution of VMM-provided values.
RSI is specified in the bitmap of those registers, but it is missing
when zeroing out those registers in the current TDX_HYPERCALL.
It was there when it was originally added in commit 752d13305c78
("x86/tdx: Expand __tdx_hypercall() to handle more arguments"), but was
later removed in commit 1e70c680375a ("x86/tdx: Do not corrupt
frame-pointer in __tdx_hypercall()"), which was correct because %rsi is
later restored in the "pop %rsi". However a later commit 7a3a401874be
("x86/tdx: Drop flags from __tdx_hypercall()") removed that "pop %rsi"
but forgot to add the "xor %rsi, %rsi" back.
Fix by adding it back.
Classification
CVE ID: CVE-2023-52874
Affected Products
Vendor: Linux
Product: Linux
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.05% (probability of being exploited)
EPSS Percentile: 17.83% (scored less or equal to compared to others)
EPSS Date: 2025-02-04 (when was this score calculated)
References
https://git.kernel.org/stable/c/2191950d35d8f81620ea8d4e04d983f664fe3a8ahttps://git.kernel.org/stable/c/de4c5bacca4f50233f1f791bec9eeb4dee1b14cd
https://git.kernel.org/stable/c/5d092b66119d774853cc9308522620299048a662