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x86/sev: Propagate #GP if getting linear instruction address failed 

When an instruction is fetched from user-space, segmentation needs to
be taken into account. This means that getting the linear address of an
instruction can fail. Hardware would raise a #GP exception in that case,
but the #VC exception handler would emulate it as a page-fault.

The insn_fetch_from_user*() functions now provide the relevant
information in case of a failure. Use that and propagate a #GP when the
linear address of an instruction to fetch could not be calculated.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210614135327.9921-7-joro@8bytes.org
This commit is contained in:
Joerg Roedel 2021-06-14 15:53:27 +02:00 committed by Borislav Petkov
parent 4aaa7eacd7
commit 07570cef5e
1 changed files with 8 additions and 1 deletions
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9
arch/x86/kernel/sev.c
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@ -261,11 +261,18 @@ static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
int insn_bytes;
insn_bytes = insn_fetch_from_user_inatomic(ctxt->regs, buffer);
if (insn_bytes <= 0) {
if (insn_bytes == 0) {
/* Nothing could be copied */
ctxt->fi.vector = X86_TRAP_PF;
ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
ctxt->fi.cr2 = ctxt->regs->ip;
return ES_EXCEPTION;
} else if (insn_bytes == -EINVAL) {
/* Effective RIP could not be calculated */
ctxt->fi.vector = X86_TRAP_GP;
ctxt->fi.error_code = 0;
ctxt->fi.cr2 = 0;
return ES_EXCEPTION;
}
if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, insn_bytes))