From 53a019a951fae849471e4a620948c5f6886bd1a4 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Fri, 7 Oct 2011 22:31:55 +0900 Subject: [PATCH] x86: Fix insn decoder for longer instruction Fix x86 insn decoder for hardening against invalid length instructions. This adds length checkings for each byte-read site and if it exceeds MAX_INSN_SIZE, returns immediately. This can happen when decoding user-space binary. Caller can check whether it happened by checking insn.*.got member is set or not. Signed-off-by: Masami Hiramatsu Cc: Stephane Eranian Cc: Andi Kleen Cc: acme@redhat.com Cc: ming.m.lin@intel.com Cc: robert.richter@amd.com Cc: ravitillo@lbl.gov Cc: yrl.pp-manager.tt@hitachi.com Cc: Peter Zijlstra Cc: Srikar Dronamraju Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20111007133155.10933.58577.stgit@localhost.localdomain Signed-off-by: Ingo Molnar --- arch/x86/lib/insn.c | 48 ++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 43 insertions(+), 5 deletions(-) diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c index 9f33b984d0ef..374562ed6704 100644 --- a/arch/x86/lib/insn.c +++ b/arch/x86/lib/insn.c @@ -22,14 +22,23 @@ #include #include -#define get_next(t, insn) \ - ({t r; r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; }) +/* Verify next sizeof(t) bytes can be on the same instruction */ +#define validate_next(t, insn, n) \ + ((insn)->next_byte + sizeof(t) + n - (insn)->kaddr <= MAX_INSN_SIZE) + +#define __get_next(t, insn) \ + ({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; }) + +#define __peek_nbyte_next(t, insn, n) \ + ({ t r = *(t*)((insn)->next_byte + n); r; }) -#define peek_next(t, insn) \ - ({t r; r = *(t*)insn->next_byte; r; }) +#define get_next(t, insn) \ + ({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); }) #define peek_nbyte_next(t, insn, n) \ - ({t r; r = *(t*)((insn)->next_byte + n); r; }) + ({ if (unlikely(!validate_next(t, insn, n))) goto err_out; __peek_nbyte_next(t, insn, n); }) + +#define peek_next(t, insn) peek_nbyte_next(t, insn, 0) /** * insn_init() - initialize struct insn @@ -158,6 +167,8 @@ vex_end: insn->vex_prefix.got = 1; prefixes->got = 1; + +err_out: return; } @@ -208,6 +219,9 @@ void insn_get_opcode(struct insn *insn) insn->attr = 0; /* This instruction is bad */ end: opcode->got = 1; + +err_out: + return; } /** @@ -241,6 +255,9 @@ void insn_get_modrm(struct insn *insn) if (insn->x86_64 && inat_is_force64(insn->attr)) insn->opnd_bytes = 8; modrm->got = 1; + +err_out: + return; } @@ -290,6 +307,9 @@ void insn_get_sib(struct insn *insn) } } insn->sib.got = 1; + +err_out: + return; } @@ -351,6 +371,9 @@ void insn_get_displacement(struct insn *insn) } out: insn->displacement.got = 1; + +err_out: + return; } /* Decode moffset16/32/64 */ @@ -373,6 +396,9 @@ static void __get_moffset(struct insn *insn) break; } insn->moffset1.got = insn->moffset2.got = 1; + +err_out: + return; } /* Decode imm v32(Iz) */ @@ -389,6 +415,9 @@ static void __get_immv32(struct insn *insn) insn->immediate.nbytes = 4; break; } + +err_out: + return; } /* Decode imm v64(Iv/Ov) */ @@ -411,6 +440,9 @@ static void __get_immv(struct insn *insn) break; } insn->immediate1.got = insn->immediate2.got = 1; + +err_out: + return; } /* Decode ptr16:16/32(Ap) */ @@ -432,6 +464,9 @@ static void __get_immptr(struct insn *insn) insn->immediate2.value = get_next(unsigned short, insn); insn->immediate2.nbytes = 2; insn->immediate1.got = insn->immediate2.got = 1; + +err_out: + return; } /** @@ -496,6 +531,9 @@ void insn_get_immediate(struct insn *insn) } done: insn->immediate.got = 1; + +err_out: + return; } /** -- 2.39.5