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Date: Wed, 15 May 2019 12:55:51 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Tyler Hicks <tyhicks@...onical.com>, Jiri Kosina <jkosina@...e.cz>, Ben Hutchings <ben@...adent.org.uk> Subject: [PATCH 4.4 244/266] x86/speculation/mds: Add SMT warning message From: Josh Poimboeuf <jpoimboe@...hat.com> commit 39226ef02bfb43248b7db12a4fdccb39d95318e3 upstream. MDS is vulnerable with SMT. Make that clear with a one-time printk whenever SMT first gets enabled. Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com> Signed-off-by: Thomas Gleixner <tglx@...utronix.de> Reviewed-by: Tyler Hicks <tyhicks@...onical.com> Acked-by: Jiri Kosina <jkosina@...e.cz> Signed-off-by: Ben Hutchings <ben@...adent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/x86/kernel/cpu/bugs.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -646,6 +646,9 @@ static void update_indir_branch_cond(voi static_branch_disable(&switch_to_cond_stibp); } +#undef pr_fmt +#define pr_fmt(fmt) fmt + /* Update the static key controlling the MDS CPU buffer clear in idle */ static void update_mds_branch_idle(void) { @@ -666,6 +669,8 @@ static void update_mds_branch_idle(void) static_branch_disable(&mds_idle_clear); } +#define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n" + void arch_smt_update(void) { /* Enhanced IBRS implies STIBP. No update required. */ @@ -689,6 +694,8 @@ void arch_smt_update(void) switch (mds_mitigation) { case MDS_MITIGATION_FULL: case MDS_MITIGATION_VMWERV: + if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY)) + pr_warn_once(MDS_MSG_SMT); update_mds_branch_idle(); break; case MDS_MITIGATION_OFF: @@ -1069,6 +1076,7 @@ static void __init l1tf_select_mitigatio setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV); } #undef pr_fmt +#define pr_fmt(fmt) fmt #ifdef CONFIG_SYSFS
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