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 <masami.hiramatsu.pt@hitachi.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
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 <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20111007133155.10933.58577.stgit@localhost.localdomain
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 9f33b98..374562e 100644
--- a/arch/x86/lib/insn.c
+++ b/arch/x86/lib/insn.c
@@ -22,14 +22,23 @@
#include <asm/inat.h>
#include <asm/insn.h>
-#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 peek_next(t, insn) \
- ({t r; r = *(t*)insn->next_byte; r; })
+#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 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 @@
insn->vex_prefix.got = 1;
prefixes->got = 1;
+
+err_out:
return;
}
@@ -208,6 +219,9 @@
insn->attr = 0; /* This instruction is bad */
end:
opcode->got = 1;
+
+err_out:
+ return;
}
/**
@@ -241,6 +255,9 @@
if (insn->x86_64 && inat_is_force64(insn->attr))
insn->opnd_bytes = 8;
modrm->got = 1;
+
+err_out:
+ return;
}
@@ -290,6 +307,9 @@
}
}
insn->sib.got = 1;
+
+err_out:
+ return;
}
@@ -351,6 +371,9 @@
}
out:
insn->displacement.got = 1;
+
+err_out:
+ return;
}
/* Decode moffset16/32/64 */
@@ -373,6 +396,9 @@
break;
}
insn->moffset1.got = insn->moffset2.got = 1;
+
+err_out:
+ return;
}
/* Decode imm v32(Iz) */
@@ -389,6 +415,9 @@
insn->immediate.nbytes = 4;
break;
}
+
+err_out:
+ return;
}
/* Decode imm v64(Iv/Ov) */
@@ -411,6 +440,9 @@
break;
}
insn->immediate1.got = insn->immediate2.got = 1;
+
+err_out:
+ return;
}
/* Decode ptr16:16/32(Ap) */
@@ -432,6 +464,9 @@
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 @@
}
done:
insn->immediate.got = 1;
+
+err_out:
+ return;
}
/**
