Commit 63e44bc5 authored by Joerg Roedel's avatar Joerg Roedel Committed by Borislav Petkov (AMD)
Browse files

x86/sev: Check for user-space IOIO pointing to kernel space 



Check the memory operand of INS/OUTS before emulating the instruction.
The #VC exception can get raised from user-space, but the memory operand
can be manipulated to access kernel memory before the emulation actually
begins and after the exception handler has run.

  [ bp: Massage commit message. ]

Fixes: 597cfe48 ("x86/boot/compressed/64: Setup a GHCB-based VC Exception handler")
Reported-by: default avatarTom Dohrmann <erbse.13@gmx.de>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
parent b9cb9c45

arch/x86/boot/compressed/sev.c

+5 −0
Original line number Diff line number Diff line
@@ -108,6 +108,11 @@ static enum es_result vc_ioio_check(struct es_em_ctxt *ctxt, u16 port, size_t si 
	return ES_OK;

}



static bool fault_in_kernel_space(unsigned long address)

{

	return false;

}



#undef __init

#define __init

arch/x86/kernel/sev-shared.c

+29 −2
Original line number Diff line number Diff line
@@ -592,6 +592,23 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) 
	sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);

}



static enum es_result vc_insn_string_check(struct es_em_ctxt *ctxt,

					   unsigned long address,

					   bool write)

{

	if (user_mode(ctxt->regs) && fault_in_kernel_space(address)) {

		ctxt->fi.vector     = X86_TRAP_PF;

		ctxt->fi.error_code = X86_PF_USER;

		ctxt->fi.cr2        = address;

		if (write)

			ctxt->fi.error_code |= X86_PF_WRITE;



		return ES_EXCEPTION;

	}



	return ES_OK;

}



static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt,

					  void *src, char *buf,

					  unsigned int data_size,
@@ -599,7 +616,12 @@ static enum es_result vc_insn_string_read(struct es_em_ctxt *ctxt, 
					  bool backwards)

{

	int i, b = backwards ? -1 : 1;

	enum es_result ret = ES_OK;

	unsigned long address = (unsigned long)src;

	enum es_result ret;



	ret = vc_insn_string_check(ctxt, address, false);

	if (ret != ES_OK)

		return ret;



	for (i = 0; i < count; i++) {

		void *s = src + (i * data_size * b);
@@ -620,7 +642,12 @@ static enum es_result vc_insn_string_write(struct es_em_ctxt *ctxt, 
					   bool backwards)

{

	int i, s = backwards ? -1 : 1;

	enum es_result ret = ES_OK;

	unsigned long address = (unsigned long)dst;

	enum es_result ret;



	ret = vc_insn_string_check(ctxt, address, true);

	if (ret != ES_OK)

		return ret;



	for (i = 0; i < count; i++) {

		void *d = dst + (i * data_size * s);