From: Joerg Roedel <joro@8bytes.org>
To: x86@kernel.org
Cc: Joerg Roedel <joro@8bytes.org>, Joerg Roedel <jroedel@suse.de>,
Andy Lutomirski <luto@kernel.org>,
stable@vger.kernel.org, hpa@zytor.com,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Jiri Slaby <jslaby@suse.cz>,
Dan Williams <dan.j.williams@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Juergen Gross <jgross@suse.com>,
Kees Cook <keescook@chromium.org>,
David Rientjes <rientjes@google.com>,
Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Mike Stunes <mstunes@vmware.com>,
Sean Christopherson <seanjc@google.com>,
Martin Radev <martin.b.radev@gmail.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: [PATCH 2/3] x86/sev-es: Check if regs->sp is trusted before adjusting #VC IST stack
Date: Wed, 17 Feb 2021 13:01:42 +0100 [thread overview]
Message-ID: <20210217120143.6106-3-joro@8bytes.org> (raw)
In-Reply-To: <20210217120143.6106-1-joro@8bytes.org>
From: Joerg Roedel <jroedel@suse.de>
The code in the NMI handler to adjust the #VC handler IST stack is
needed in case an NMI hits when the #VC handler is still using its IST
stack.
But the check for this condition also needs to look if the regs->sp
value is trusted, meaning it was not set by user-space. Extend the
check to not use regs->sp when the NMI interrupted user-space code or
the SYSCALL gap.
Reported-by: Andy Lutomirski <luto@kernel.org>
Fixes: 315562c9af3d5 ("x86/sev-es: Adjust #VC IST Stack on entering NMI handler")
Cc: stable@vger.kernel.org # 5.10+
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/kernel/sev-es.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 84c1821819af..0df38b185d53 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -144,7 +144,9 @@ void noinstr __sev_es_ist_enter(struct pt_regs *regs)
old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]);
/* Make room on the IST stack */
- if (on_vc_stack(regs->sp))
+ if (on_vc_stack(regs->sp) &&
+ !user_mode(regs) &&
+ !from_syscall_gap(regs))
new_ist = ALIGN_DOWN(regs->sp, 8) - sizeof(old_ist);
else
new_ist = old_ist - sizeof(old_ist);
--
2.30.0
next prev parent reply other threads:[~2021-02-17 12:08 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 12:01 [PATCH 0/3] x86/sev-es: Check for trusted regs->sp in __sev_es_ist_enter() Joerg Roedel
2021-02-17 12:01 ` [PATCH 1/3] x86/sev-es: Introduce from_syscall_gap() helper Joerg Roedel
2021-02-17 17:59 ` Borislav Petkov
2021-02-17 12:01 ` Joerg Roedel [this message]
2021-02-17 18:00 ` [PATCH 2/3] x86/sev-es: Check if regs->sp is trusted before adjusting #VC IST stack Borislav Petkov
2021-02-17 18:09 ` Andy Lutomirski
2021-02-18 11:25 ` Joerg Roedel
2021-02-18 17:49 ` Andy Lutomirski
2021-02-18 19:21 ` Joerg Roedel
2021-02-19 0:28 ` Andy Lutomirski
2021-02-19 11:05 ` Joerg Roedel
2021-02-17 12:01 ` [PATCH 3/3] x86/sev-es: Improve comments in and around __sev_es_ist_enter/exit() Joerg Roedel
2021-02-17 18:00 ` Borislav Petkov
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