diff options
| author | Borislav Petkov (AMD) | 2023-10-05 11:06:36 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2023-10-25 12:03:04 +0200 |
| commit | 95ff590b802757f8b6bd32e7e5b21ef9b91e2583 (patch) | |
| tree | 2afe8a023260de04baf67de54895f3acdd040a41 | |
| parent | 19ffa9b2515a60c79202872098c0c9ba519062cc (diff) | |
x86/sev: Disable MMIO emulation from user mode
Upstream commit: a37cd2a59d0cb270b1bba568fd3a3b8668b9d3ba
A virt scenario can be constructed where MMIO memory can be user memory.
When that happens, a race condition opens between when the hardware
raises the #VC and when the #VC handler gets to emulate the instruction.
If the MOVS is replaced with a MOVS accessing kernel memory in that
small race window, then write to kernel memory happens as the access
checks are not done at emulation time.
Disable MMIO emulation in user mode temporarily until a sensible use
case appears and justifies properly handling the race window.
Fixes: 0118b604c2c9 ("x86/sev-es: Handle MMIO String Instructions")
Reported-by: Tom Dohrmann <erbse.13@gmx.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Tom Dohrmann <erbse.13@gmx.de>
Cc: <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/kernel/sev.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index afda719dd725..6a8668efd662 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -1552,6 +1552,9 @@ static enum es_result vc_handle_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt) return ES_DECODE_FAILED; } + if (user_mode(ctxt->regs)) + return ES_UNSUPPORTED; + switch (mmio) { case MMIO_WRITE: memcpy(ghcb->shared_buffer, reg_data, bytes); |