linux-kernel - [PATCH -tip ] x86: Handle failures of getting immediates in instruction decoder

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Message-ID: <20120413032427.32577.42602.stgit@localhost.localdomain>
Date:	Fri, 13 Apr 2012 12:24:27 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Prashanth Nageshappa <prashanth@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Oleg Nesterov <oleg@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Anton Arapov <anton@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	yrl.pp-manager.tt@...achi.com,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: [PATCH -tip ] x86: Handle failures of getting immediates in
 instruction decoder

Correctly handle failures when getting immediate operands
in x86 instruction decoder. This can be happen if the
instruction is badly longer than maximum length, or
insn->opnd_bytes is manually changed.

This patch also fixes warnings from -Wswitch-default flag.

Reported-by: Prashanth Nageshappa <prashanth@...ux.vnet.ibm.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
---

 arch/x86/lib/insn.c |   53 +++++++++++++++++++++++++++++++++++----------------
 1 files changed, 36 insertions(+), 17 deletions(-)

diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 25feb1a..b1e6c4b 100644
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -379,8 +379,8 @@ err_out:
 	return;
 }
 
-/* Decode moffset16/32/64 */
-static void __get_moffset(struct insn *insn)
+/* Decode moffset16/32/64. Return 0 if failed */
+static int __get_moffset(struct insn *insn)
 {
 	switch (insn->addr_bytes) {
 	case 2:
@@ -397,15 +397,19 @@ static void __get_moffset(struct insn *insn)
 		insn->moffset2.value = get_next(int, insn);
 		insn->moffset2.nbytes = 4;
 		break;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
 	}
 	insn->moffset1.got = insn->moffset2.got = 1;
 
+	return 1;
+
 err_out:
-	return;
+	return 0;
 }
 
-/* Decode imm v32(Iz) */
-static void __get_immv32(struct insn *insn)
+/* Decode imm v32(Iz). Return 0 if failed */
+static int __get_immv32(struct insn *insn)
 {
 	switch (insn->opnd_bytes) {
 	case 2:
@@ -417,14 +421,18 @@ static void __get_immv32(struct insn *insn)
 		insn->immediate.value = get_next(int, insn);
 		insn->immediate.nbytes = 4;
 		break;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
 	}
 
+	return 1;
+
 err_out:
-	return;
+	return 0;
 }
 
-/* Decode imm v64(Iv/Ov) */
-static void __get_immv(struct insn *insn)
+/* Decode imm v64(Iv/Ov), Return 0 if failed */
+static int __get_immv(struct insn *insn)
 {
 	switch (insn->opnd_bytes) {
 	case 2:
@@ -441,15 +449,18 @@ static void __get_immv(struct insn *insn)
 		insn->immediate2.value = get_next(int, insn);
 		insn->immediate2.nbytes = 4;
 		break;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
 	}
 	insn->immediate1.got = insn->immediate2.got = 1;
 
+	return 1;
 err_out:
-	return;
+	return 0;
 }
 
 /* Decode ptr16:16/32(Ap) */
-static void __get_immptr(struct insn *insn)
+static int __get_immptr(struct insn *insn)
 {
 	switch (insn->opnd_bytes) {
 	case 2:
@@ -462,14 +473,17 @@ static void __get_immptr(struct insn *insn)
 		break;
 	case 8:
 		/* ptr16:64 is not exist (no segment) */
-		return;
+		return 0;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
 	}
 	insn->immediate2.value = get_next(unsigned short, insn);
 	insn->immediate2.nbytes = 2;
 	insn->immediate1.got = insn->immediate2.got = 1;
 
+	return 1;
 err_out:
-	return;
+	return 0;
 }
 
 /**
@@ -489,7 +503,8 @@ void insn_get_immediate(struct insn *insn)
 		insn_get_displacement(insn);
 
 	if (inat_has_moffset(insn->attr)) {
-		__get_moffset(insn);
+		if (!__get_moffset(insn))
+			goto err_out;
 		goto done;
 	}
 
@@ -517,16 +532,20 @@ void insn_get_immediate(struct insn *insn)
 		insn->immediate2.nbytes = 4;
 		break;
 	case INAT_IMM_PTR:
-		__get_immptr(insn);
+		if (!__get_immptr(insn))
+			goto err_out;
 		break;
 	case INAT_IMM_VWORD32:
-		__get_immv32(insn);
+		if (!__get_immv32(insn))
+			goto err_out;
 		break;
 	case INAT_IMM_VWORD:
-		__get_immv(insn);
+		if (!__get_immv(insn))
+			goto err_out;
 		break;
 	default:
-		break;
+		/* Here, insn must have an immediate, but failed */
+		goto err_out;
 	}
 	if (inat_has_second_immediate(insn->attr)) {
 		insn->immediate2.value = get_next(char, insn);

--
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