linux-kernel - [RFC PATCH v0 04/19] x86/insn-eval: Handle return values from the decoder

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Date:   Tue, 24 Nov 2020 11:19:37 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Lutomirski <luto@...capital.net>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH v0 04/19] x86/insn-eval: Handle return values from the decoder

From: Borislav Petkov <bp@...e.de>

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

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/lib/insn-eval.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
index 99fafbaf8555..5825b4cf4386 100644
--- a/arch/x86/lib/insn-eval.c
+++ b/arch/x86/lib/insn-eval.c
@@ -1117,7 +1117,8 @@ static int get_eff_addr_sib(struct insn *insn, struct pt_regs *regs,
 	if (insn->addr_bytes != 8 && insn->addr_bytes != 4)
 		return -EINVAL;
 
-	insn_get_modrm(insn);
+	if (insn_get_modrm(insn))
+		return -EINVAL;
 
 	if (!insn->modrm.nbytes)
 		return -EINVAL;
@@ -1125,7 +1126,8 @@ 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);
+	if (insn_get_sib(insn))
+		return -EINVAL;
 
 	if (!insn->sib.nbytes)
 		return -EINVAL;
@@ -1194,8 +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_modrm(insn) || insn_get_displacement(insn))
+		goto out;
 
 	if (insn->addr_bytes != 2)
 		goto out;
@@ -1491,7 +1493,9 @@ bool insn_decode_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;
 
-- 
2.21.0