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x86: Fix insn decoder for longer instruction

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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>
This commit is contained in:
Masami Hiramatsu 2011-10-07 22:31:55 +09:00 committed by Ingo Molnar
parent 65112dccf8
commit 53a019a951
1 changed files with 43 additions and 5 deletions
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48
arch/x86/lib/insn.c
View File

@ -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 @@ 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;
}
/**