x86/bugs: Report Intel retbleed vulnerability

[mirror_ubuntu-jammy-kernel.git] / arch / x86 / kernel / cpu / bugs.c

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b002005820def03fdc00059165f3b1fcd5fc79a1..b82d1139422c932761ca0f2d20bcdcd42d15c443 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -783,12 +783,17 @@ static int __init nospectre_v1_cmdline(char *str)
 }
 early_param("nospectre_v1", nospectre_v1_cmdline);
 
+static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
+       SPECTRE_V2_NONE;
+
 #undef pr_fmt
 #define pr_fmt(fmt)     "RETBleed: " fmt
 
 enum retbleed_mitigation {
        RETBLEED_MITIGATION_NONE,
        RETBLEED_MITIGATION_UNRET,
+       RETBLEED_MITIGATION_IBRS,
+       RETBLEED_MITIGATION_EIBRS,
 };
 
 enum retbleed_mitigation_cmd {
@@ -800,6 +805,8 @@ enum retbleed_mitigation_cmd {
 const char * const retbleed_strings[] = {
        [RETBLEED_MITIGATION_NONE]      = "Vulnerable",
        [RETBLEED_MITIGATION_UNRET]     = "Mitigation: untrained return thunk",
+       [RETBLEED_MITIGATION_IBRS]      = "Mitigation: IBRS",
+       [RETBLEED_MITIGATION_EIBRS]     = "Mitigation: Enhanced IBRS",
 };
 
 static enum retbleed_mitigation retbleed_mitigation __ro_after_init =
@@ -842,6 +849,7 @@ early_param("retbleed", retbleed_parse_cmdline);
 
 #define RETBLEED_UNTRAIN_MSG "WARNING: BTB untrained return thunk mitigation is only effective on AMD/Hygon!\n"
 #define RETBLEED_COMPILER_MSG "WARNING: kernel not compiled with RETPOLINE or -mfunction-return capable compiler!\n"
+#define RETBLEED_INTEL_MSG "WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible!\n"
 
 static void __init retbleed_select_mitigation(void)
 {
@@ -858,12 +866,15 @@ static void __init retbleed_select_mitigation(void)
 
        case RETBLEED_CMD_AUTO:
        default:
-               if (!boot_cpu_has_bug(X86_BUG_RETBLEED))
-                       break;
-
                if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
                    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
                        retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
+
+               /*
+                * The Intel mitigation (IBRS) was already selected in
+                * spectre_v2_select_mitigation().
+                */
+
                break;
        }
 
@@ -893,15 +904,31 @@ static void __init retbleed_select_mitigation(void)
                break;
        }
 
+       /*
+        * Let IBRS trump all on Intel without affecting the effects of the
+        * retbleed= cmdline option.
+        */
+       if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
+               switch (spectre_v2_enabled) {
+               case SPECTRE_V2_IBRS:
+                       retbleed_mitigation = RETBLEED_MITIGATION_IBRS;
+                       break;
+               case SPECTRE_V2_EIBRS:
+               case SPECTRE_V2_EIBRS_RETPOLINE:
+               case SPECTRE_V2_EIBRS_LFENCE:
+                       retbleed_mitigation = RETBLEED_MITIGATION_EIBRS;
+                       break;
+               default:
+                       pr_err(RETBLEED_INTEL_MSG);
+               }
+       }
+
        pr_info("%s\n", retbleed_strings[retbleed_mitigation]);
 }
 
 #undef pr_fmt
 #define pr_fmt(fmt)     "Spectre V2 : " fmt
 
-static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
-       SPECTRE_V2_NONE;
-
 static enum spectre_v2_user_mitigation spectre_v2_user_stibp __ro_after_init =
        SPECTRE_V2_USER_NONE;
 static enum spectre_v2_user_mitigation spectre_v2_user_ibpb __ro_after_init =