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   1 From leitao@debian.org  Fri Jun 20 16:37:13 2025
   2 From: Breno Leitao <leitao@debian.org>
   3 Date: Fri, 20 Jun 2025 06:51:23 -0700
   4 Subject: Revert "x86/bugs: Make spectre user default depend on MITIGATION_SPECTRE_V2" on v6.6 and older
   5 To: Jonathan Corbet <corbet@lwn.net>, Thomas Gleixner <tglx@linutronix.de>,  Borislav Petkov <bp@alien8.de>, Peter Zijlstra <peterz@infradead.org>,  Josh Poimboeuf <jpoimboe@kernel.org>,  Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,  Ingo Molnar <mingo@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>,  x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>, stable@vger.kernel.org
   6 Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,  kernel-team@meta.com, David.Kaplan@amd.com, mingo@kernel.org,  brad.spengler@opensrcsec.com, Brad Spengler <brad.spengler@opensrcsec.com>,  Salvatore Bonaccorso <carnil@debian.org>, Breno Leitao <leitao@debian.org>
   7 Message-ID: <20250620-stable_revert_66-v1-1-841800dd2c68@debian.org>
   8
   9 From: Breno Leitao <leitao@debian.org>
  10
  11 This reverts commit a8c22ec36cdd99c1002d7152f859798fef7c4d58 which is
  12 commit 98fdaeb296f51ef08e727a7cc72e5b5c864c4f4d upstream.
  13
  14 commit 7adb96687ce8 ("x86/bugs: Make spectre user default depend on
  15 MITIGATION_SPECTRE_V2") depends on commit 72c70f480a70 ("x86/bugs: Add
  16 a separate config for Spectre V2"), which introduced
  17 MITIGATION_SPECTRE_V2.
  18
  19 commit 72c70f480a70 ("x86/bugs: Add a separate config for Spectre V2")
  20 never landed in stable tree, thus, stable tree doesn't have
  21 MITIGATION_SPECTRE_V2, that said, commit 7adb96687ce8 ("x86/bugs: Make
  22 spectre user default depend on MITIGATION_SPECTRE_V2") has no value if
  23 the dependecy was not applied.
  24
  25 Revert commit 7adb96687ce8 ("x86/bugs: Make spectre user default
  26 depend on MITIGATION_SPECTRE_V2")  in stable kernel which landed in in
  27 5.4.294, 5.10.238, 5.15.185, 6.1.141 and 6.6.93 stable versions.
  28
  29 Cc: David.Kaplan@amd.com
  30 Cc: peterz@infradead.org
  31 Cc: pawan.kumar.gupta@linux.intel.com
  32 Cc: mingo@kernel.org
  33 Cc: brad.spengler@opensrcsec.com
  34 Cc: stable@vger.kernel.org # 6.6 6.1 5.15 5.10 5.4
  35 Reported-by: Brad Spengler <brad.spengler@opensrcsec.com>
  36 Reported-by: Salvatore Bonaccorso <carnil@debian.org>
  37 Signed-off-by: Breno Leitao <leitao@debian.org>
  38 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  39 ---
  40  Documentation/admin-guide/kernel-parameters.txt |    2 --
  41  arch/x86/kernel/cpu/bugs.c                      |   10 +++-------
  42  2 files changed, 3 insertions(+), 9 deletions(-)
  43
  44 --- a/Documentation/admin-guide/kernel-parameters.txt
  45 +++ b/Documentation/admin-guide/kernel-parameters.txt
  46 @@ -4600,8 +4600,6 @@
  47
  48                         Selecting 'on' will also enable the mitigation
  49                         against user space to user space task attacks.
  50 -                       Selecting specific mitigation does not force enable
  51 -                       user mitigations.
  52
  53                         Selecting 'off' will disable both the kernel and
  54                         the user space protections.
  55 --- a/arch/x86/kernel/cpu/bugs.c
  56 +++ b/arch/x86/kernel/cpu/bugs.c
  57 @@ -1050,13 +1050,9 @@ static __ro_after_init enum spectre_v2_m
  58  static enum spectre_v2_user_cmd __init
  59  spectre_v2_parse_user_cmdline(void)
  60  {
  61 -       enum spectre_v2_user_cmd mode;
  62         char arg[20];
  63         int ret, i;
  64
  65 -       mode = IS_ENABLED(CONFIG_MITIGATION_SPECTRE_V2) ?
  66 -               SPECTRE_V2_USER_CMD_AUTO : SPECTRE_V2_USER_CMD_NONE;
  67 -
  68         switch (spectre_v2_cmd) {
  69         case SPECTRE_V2_CMD_NONE:
  70                 return SPECTRE_V2_USER_CMD_NONE;
  71 @@ -1069,7 +1065,7 @@ spectre_v2_parse_user_cmdline(void)
  72         ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
  73                                   arg, sizeof(arg));
  74         if (ret < 0)
  75 -               return mode;
  76 +               return SPECTRE_V2_USER_CMD_AUTO;
  77
  78         for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
  79                 if (match_option(arg, ret, v2_user_options[i].option)) {
  80 @@ -1079,8 +1075,8 @@ spectre_v2_parse_user_cmdline(void)
  81                 }
  82         }
  83
  84 -       pr_err("Unknown user space protection option (%s). Switching to default\n", arg);
  85 -       return mode;
  86 +       pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg);
  87 +       return SPECTRE_V2_USER_CMD_AUTO;
  88  }
  89
  90  static inline bool spectre_v2_in_eibrs_mode(enum spectre_v2_mitigation mode)