Commit 6e8c83d2 authored by Borislav Petkov's avatar Borislav Petkov
Browse files

x86/insn-eval: Handle return values from the decoder 



Now that the different instruction-inspecting functions return a value,
test that and return early from callers if error has been encountered.

While at it, do not call insn_get_modrm() when calling
insn_get_displacement() because latter will make sure to call
insn_get_modrm() if ModRM hasn't been parsed yet.

Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210304174237.31945-6-bp@alien8.de
parent 93281c4a

arch/x86/lib/insn-eval.c

+21 −13
Original line number Diff line number Diff line
@@ -924,10 +924,11 @@ static int get_seg_base_limit(struct insn *insn, struct pt_regs *regs, 
static int get_eff_addr_reg(struct insn *insn, struct pt_regs *regs,

			    int *regoff, long *eff_addr)

{

	insn_get_modrm(insn);

	int ret;



	if (!insn->modrm.nbytes)

		return -EINVAL;

	ret = insn_get_modrm(insn);

	if (ret)

		return ret;



	if (X86_MODRM_MOD(insn->modrm.value) != 3)

		return -EINVAL;
@@ -973,14 +974,14 @@ static int get_eff_addr_modrm(struct insn *insn, struct pt_regs *regs, 
			      int *regoff, long *eff_addr)

{

	long tmp;

	int ret;



	if (insn->addr_bytes != 8 && insn->addr_bytes != 4)

		return -EINVAL;



	insn_get_modrm(insn);



	if (!insn->modrm.nbytes)

		return -EINVAL;

	ret = insn_get_modrm(insn);

	if (ret)

		return ret;



	if (X86_MODRM_MOD(insn->modrm.value) > 2)

		return -EINVAL;
@@ -1102,18 +1103,21 @@ static int get_eff_addr_modrm_16(struct insn *insn, struct pt_regs *regs, 
 * @base_offset will have a register, as an offset from the base of pt_regs,

 * that can be used to resolve the associated segment.

 *

 * -EINVAL on error.

 * Negative value on error.

 */

static int get_eff_addr_sib(struct insn *insn, struct pt_regs *regs,

			    int *base_offset, long *eff_addr)

{

	long base, indx;

	int indx_offset;

	int ret;



	if (insn->addr_bytes != 8 && insn->addr_bytes != 4)

		return -EINVAL;



	insn_get_modrm(insn);

	ret = insn_get_modrm(insn);

	if (ret)

		return ret;



	if (!insn->modrm.nbytes)

		return -EINVAL;
@@ -1121,7 +1125,9 @@ static int get_eff_addr_sib(struct insn *insn, struct pt_regs *regs, 
	if (X86_MODRM_MOD(insn->modrm.value) > 2)

		return -EINVAL;



	insn_get_sib(insn);

	ret = insn_get_sib(insn);

	if (ret)

		return ret;



	if (!insn->sib.nbytes)

		return -EINVAL;
@@ -1190,8 +1196,8 @@ static void __user *get_addr_ref_16(struct insn *insn, struct pt_regs *regs) 
	short eff_addr;

	long tmp;



	insn_get_modrm(insn);

	insn_get_displacement(insn);

	if (insn_get_displacement(insn))

		goto out;



	if (insn->addr_bytes != 2)

		goto out;
@@ -1525,7 +1531,9 @@ bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs, 
	insn->addr_bytes = INSN_CODE_SEG_ADDR_SZ(seg_defs);

	insn->opnd_bytes = INSN_CODE_SEG_OPND_SZ(seg_defs);



	insn_get_length(insn);

	if (insn_get_length(insn))

		return false;



	if (buf_size < insn->length)

		return false;