linux/arch/x86/tools
Dave Hansen 6ba48ff46f x86: Remove arbitrary instruction size limit in instruction decoder
The current x86 instruction decoder steps along through the
instruction stream but always ensures that it never steps farther
than the largest possible instruction size (MAX_INSN_SIZE).

The MPX code is now going to be doing some decoding of userspace
instructions.  We copy those from userspace in to the kernel and
they're obviously completely untrusted coming from userspace.  In
addition to the constraint that instructions can only be so long,
we also have to be aware of how long the buffer is that came in
from userspace.  This _looks_ to be similar to what the perf and
kprobes is doing, but it's unclear to me whether they are
affected.

The whole reason we need this is that it is perfectly valid to be
executing an instruction within MAX_INSN_SIZE bytes of an
unreadable page. We should be able to gracefully handle short
reads in those cases.

This adds support to the decoder to record how long the buffer
being decoded is and to refuse to "validate" the instruction if
we would have gone over the end of the buffer to decode it.

The kprobes code probably needs to be looked at here a bit more
carefully.  This patch still respects the MAX_INSN_SIZE limit
there but the kprobes code does look like it might be able to
be a bit more strict than it currently is.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Jim Keniston <jkenisto@us.ibm.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: x86@kernel.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Link: http://lkml.kernel.org/r/20141114153957.E6B01535@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-11-18 00:58:52 +01:00
..
.gitignore x86, relocs: Refactor the relocs tool to merge 32- and 64-bit ELF 2013-04-16 16:02:58 -07:00
chkobjdump.awk x86: Fix objdump version check in chkobjdump.awk for different formats. 2009-12-18 09:26:56 -08:00
distill.awk x86: Show symbol name if insn decoder test failed 2009-11-17 07:16:50 +01:00
gen-insn-attr-x86.awk x86, insn: Add new opcodes as of June, 2013 2013-08-06 08:08:47 -07:00
insn_sanity.c x86: Remove arbitrary instruction size limit in instruction decoder 2014-11-18 00:58:52 +01:00
Makefile x86/build: Supress "Nothing to be done for ..." messages 2014-04-14 11:44:36 +02:00
relocs_32.c x86, relocs: Refactor the relocs tool to merge 32- and 64-bit ELF 2013-04-16 16:02:58 -07:00
relocs_64.c x86, relocs: Refactor the relocs tool to merge 32- and 64-bit ELF 2013-04-16 16:02:58 -07:00
relocs_common.c x86, relocs: Add manual debug mode 2014-01-22 04:21:45 -08:00
relocs.c x86/relocs: Make per_cpu_load_addr static 2014-09-24 15:17:47 +02:00
relocs.h x86, relocs: Add manual debug mode 2014-01-22 04:21:45 -08:00
test_get_len.c x86: Remove arbitrary instruction size limit in instruction decoder 2014-11-18 00:58:52 +01:00