From: Hyunwook (Wooky) Baek baekhw@google.com
commit 7024f60d655272bd2ca1d3a4c9e0a63319b1eea1 upstream.
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.
When invoking INSB/OUTSB instructions in kernel space in a SEV-ES-enabled VM, the kernel crashes with the following message:
"SEV-ES: Unsupported exception in #VC instruction emulation - can't continue"
Handle that case properly.
[ bp: Massage commit message. ]
Fixes: f980f9c31a92 ("x86/sev-es: Compile early handler code into kernel image") Signed-off-by: Hyunwook (Wooky) Baek baekhw@google.com Signed-off-by: Borislav Petkov bp@suse.de Acked-by: David Rientjes rientjes@google.com Link: https://lkml.kernel.org/r/20210110071102.2576186-1-baekhw@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/sev-es.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
--- 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(struc 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 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))