[PATCH 5.10 018/130] x86/insn-eval: Handle return values from the decoder

Greg Kroah-Hartman
2022-07-12T18:41:33Z

From: Borislav Petkov <bp@suse.de>

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>
---
arch/x86/lib/insn-eval.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)

--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -928,10 +928,11 @@ static int get_seg_base_limit(struct ins
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 ins
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
* @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
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(stru
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->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;