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authorJoerg Roedel <jroedel@suse.de>2021-03-03 15:17:13 +0100
committerBorislav Petkov <bp@suse.de>2021-03-09 12:26:26 +0100
commit545ac14c16b5dbd909d5a90ddf5b5a629a40fa94 (patch)
tree180b58a5e4ddb5386be43f5fd8d473d9c5955e9d
parentx86/sev-es: Introduce ip_within_syscall_gap() helper (diff)
downloadlinux-545ac14c16b5dbd909d5a90ddf5b5a629a40fa94.tar.xz
linux-545ac14c16b5dbd909d5a90ddf5b5a629a40fa94.zip
x86/sev-es: Check regs->sp is trusted before adjusting #VC IST stack
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@kernel.org> Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: stable@vger.kernel.org # 5.10+ Link: https://lkml.kernel.org/r/20210303141716.29223-3-joro@8bytes.org
-rw-r--r--arch/x86/kernel/sev-es.c14
1 files 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);