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 5.11-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-5.11 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(-) --- 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 c 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 p 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); Patches currently in stable-queue which might be from jroedel@xxxxxxx are queue-5.11/iommu-vt-d-clear-prq-overflow-only-when-prq-is-empty.patch queue-5.11/x86-sev-es-check-regs-sp-is-trusted-before-adjusting-vc-ist-stack.patch queue-5.11/iommu-amd-fix-performance-counter-initialization.patch queue-5.11/x86-sev-es-introduce-ip_within_syscall_gap-helper.patch queue-5.11/x86-sev-es-use-__copy_from_user_inatomic.patch queue-5.11/x86-sev-es-correctly-track-irq-states-in-runtime-vc-handler.patch