(2015/01/14 6:49), Andy Lutomirski wrote: > x86 instructions cannot exceed 15 bytes, and the instruction decoder > should enforce that. Prior to 6ba48ff46f76, the instruction length > limit was implicitly set to 16, which was an approximation of 15, > but there is currently no limit at all. > > Fix the decoder to reject instructions that exceed 15 bytes. > A subsequent patch (targetted for 3.20) will fix MAX_INSN_SIZE.
Hmm, is there any problem to just change MAX_INSN_SIZE to 15? > Other than potentially confusing some of the decoder sanity checks, > I'm not aware of any actual problems that omitting this check would > cause. > > Fixes: 6ba48ff46f76 x86: Remove arbitrary instruction size limit in > instruction decoder > Signed-off-by: Andy Lutomirski <[email protected]> > --- > arch/x86/lib/insn.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c > index 2480978b31cc..7b80745d2c5a 100644 > --- a/arch/x86/lib/insn.c > +++ b/arch/x86/lib/insn.c > @@ -52,6 +52,13 @@ > */ > void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64) > { > + /* > + * Instructions longer than 15 bytes are invalid even if the > + * input buffer is long enough to hold them. > + */ > + if (buf_len > 15) > + buf_len = 15; > + Without changing the MAX_INSN_SIZE, this looks very odd, since all other code suppose that the max length of an instruction is 16 (MAX_INSN_SIZE) except here. Thank you, > memset(insn, 0, sizeof(*insn)); > insn->kaddr = kaddr; > insn->end_kaddr = kaddr + buf_len; > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
