From: Kim Phillips Date: Mon, 28 Feb 2022 17:23:15 +0000 (-0600) Subject: x86/speculation: Use generic retpoline by default on AMD X-Git-Tag: v4.19.234~27 X-Git-Url: https://git.fsl.cs.sunysb.edu/?a=commitdiff_plain;h=d3cb3a6927222268a10b2f12dfb8c9444f7cc39e;p=wrapfs-5.3.y.git x86/speculation: Use generic retpoline by default on AMD commit 244d00b5dd4755f8df892c86cab35fb2cfd4f14b upstream. AMD retpoline may be susceptible to speculation. The speculation execution window for an incorrect indirect branch prediction using LFENCE/JMP sequence may potentially be large enough to allow exploitation using Spectre V2. By default, don't use retpoline,lfence on AMD. Instead, use the generic retpoline. Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index cd660aceb7c6..70ab182e30fb 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -898,14 +898,6 @@ static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void) return SPECTRE_V2_NONE; } - if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { - if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { - pr_err("LFENCE not serializing, switching to generic retpoline\n"); - return SPECTRE_V2_RETPOLINE; - } - return SPECTRE_V2_LFENCE; - } - return SPECTRE_V2_RETPOLINE; }