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

Masami Hiramatsu
2012-04-13T03:24:27Z

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@linux.vnet.ibm.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.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);