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

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>

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 3a7e307d42aa97e4f19bbc389daba741c3938d31..ffc8b7dcf1feb987cf2ff89cdee41b8921437028 100644 (file)
--- 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 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;