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Date: Sat, 9 Jan 2021 23:11:02 -0800 From: "Hyunwook (Wooky) Baek" <baekhw@...gle.com> To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de> Cc: Joerg Roedel <jroedel@...e.de>, Tom Lendacky <thomas.lendacky@....com>, David Rientjes <rientjes@...gle.com>, Sean Christopherson <seanjc@...gle.com>, linux-kernel@...r.kernel.org, x86@...nel.org, "Hyunwook (Wooky) Baek" <baekhw@...gle.com> Subject: [PATCH V2] x86/sev-es: Fix SEV-ES #VC handler for string port IO Don't assume dest/source buffers are userspace addresses when manually copying data for string I/O or MOVS MMIO, as {get,put}_user() will fail if handed a kernel address and ultimately lead to a kernel panic. Signed-off-by: Hyunwook (Wooky) Baek <baekhw@...gle.com> Acked-by: David Rientjes <rientjes@...gle.com> --- This patch is tested by invoking INSB/OUTSB instructions in kernel space in a SEV-ES-enabled VM. Without the patch, the kernel crashed with the following message: "SEV-ES: Unsupported exception in #VC instruction emulation - can't continue" With the patch, the instructions successfully read/wrote the string from/to the I/O port. arch/x86/kernel/sev-es.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c index 0bd1a0fc587e..ab31c34ba508 100644 --- a/arch/x86/kernel/sev-es.c +++ b/arch/x86/kernel/sev-es.c @@ -286,6 +286,12 @@ static enum es_result vc_write_mem(struct es_em_ctxt *ctxt, u16 d2; u8 d1; + /* If instruction ran in kernel mode and the I/O buffer is in kernel space */ + if (!user_mode(ctxt->regs) && !access_ok(target, size)) { + memcpy(dst, buf, size); + return ES_OK; + } + switch (size) { case 1: memcpy(&d1, buf, 1); @@ -335,6 +341,12 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt, u16 d2; u8 d1; + /* If instruction ran in kernel mode and the I/O buffer is in kernel space */ + if (!user_mode(ctxt->regs) && !access_ok(s, size)) { + memcpy(buf, src, size); + return ES_OK; + } + switch (size) { case 1: if (get_user(d1, s)) -- 2.30.0.284.gd98b1dd5eaa7-goog
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