This is a note to let you know that I've just added the patch titled
x86/sev-es: Check regs->sp is trusted before adjusting #VC IST stack
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-sev-es-check-regs-sp-is-trusted-before-adjusting-vc-ist-stack.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 545ac14c16b5dbd909d5a90ddf5b5a629a40fa94 Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@xxxxxxx>
Date: Wed, 3 Mar 2021 15:17:13 +0100
Subject: x86/sev-es: Check regs->sp is trusted before adjusting #VC IST stack
From: Joerg Roedel <jroedel@xxxxxxx>
commit 545ac14c16b5dbd909d5a90ddf5b5a629a40fa94 upstream.
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.
Fixes: 315562c9af3d5 ("x86/sev-es: Adjust #VC IST Stack on entering NMI handler")
Reported-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 5.10+
Link: https://lkml.kernel.org/r/20210303141716.29223-3-joro@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/sev-es.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 84c1821819af..301f20f6d4dd 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -121,8 +121,18 @@ static void __init setup_vc_stacks(int cpu)
cea_set_pte((void *)vaddr, pa, PAGE_KERNEL);
}
-static __always_inline bool on_vc_stack(unsigned long sp)
+static __always_inline bool on_vc_stack(struct pt_regs *regs)
{
+ unsigned long sp = regs->sp;
+
+ /* User-mode RSP is not trusted */
+ if (user_mode(regs))
+ return false;
+
+ /* SYSCALL gap still has user-mode RSP */
+ if (ip_within_syscall_gap(regs))
+ return false;
+
return ((sp >= __this_cpu_ist_bottom_va(VC)) && (sp < __this_cpu_ist_top_va(VC)));
}
@@ -144,7 +154,7 @@ 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))
new_ist = ALIGN_DOWN(regs->sp, 8) - sizeof(old_ist);
else
new_ist = old_ist - sizeof(old_ist);
--
2.30.2
Patches currently in stable-queue which might be from jroedel@xxxxxxx are
queue-5.10/iommu-vt-d-clear-prq-overflow-only-when-prq-is-empty.patch
queue-5.10/x86-sev-es-check-regs-sp-is-trusted-before-adjusting-vc-ist-stack.patch
queue-5.10/iommu-amd-fix-performance-counter-initialization.patch
queue-5.10/x86-sev-es-introduce-ip_within_syscall_gap-helper.patch
queue-5.10/x86-sev-es-use-__copy_from_user_inatomic.patch
queue-5.10/x86-sev-es-correctly-track-irq-states-in-runtime-vc-handler.patch
