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

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commit 6e8c83d2a3afbfd5ee019ec720b75a42df515caa upstream.

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: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210304174237.31945-6-bp@alien8.de
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Borislav Petkov 2020-11-19 19:20:18 +01:00 committed by Greg Kroah-Hartman
parent 6bc6875b82
commit e6f8dc86a1
1 changed files with 21 additions and 13 deletions
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34
arch/x86/lib/insn-eval.c
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@ -928,10 +928,11 @@ 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;
@ -977,14 +978,14 @@ 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;
@ -1106,18 +1107,21 @@ 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;
@ -1125,7 +1129,9 @@ 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;
@ -1194,8 +1200,8 @@ 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;
@ -1529,7 +1535,9 @@ 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;