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authorAndy Lutomirski <luto@amacapital.net>2015-01-27 16:06:02 -0800
committerIngo Molnar <mingo@kernel.org>2015-02-19 00:01:24 +0100
commit91e5ed49fca09c2b83b262b9757d1376ee2b46c3 (patch)
tree494a1ca21a9743ec5d13b918938cc99d4ede7115 /arch/x86/lib
parentcbb53b9623a70f012e1fdfb6fc0af6878df4762b (diff)
downloadlinux-91e5ed49fca09c2b83b262b9757d1376ee2b46c3.tar.bz2
x86/asm/decoder: Fix and enforce max instruction size in the insn decoder
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 MAX_INSN_SIZE (it should be 15, not 16), and fix the decoder to reject instructions that exceed MAX_INSN_SIZE. Other than potentially confusing some of the decoder sanity checks, I'm not aware of any actual problems that omitting this check would cause, nor am I aware of any practical problems caused by the MAX_INSN_SIZE error. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Fixes: 6ba48ff46f76 ("x86: Remove arbitrary instruction size limit ... Link: http://lkml.kernel.org/r/f8f0bc9b8c58cfd6830f7d88400bf1396cbdcd0f.1422403511.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/lib')
-rw-r--r--arch/x86/lib/insn.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c
index 5ea00ddc1825..8f72b334aea0 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 MAX_INSN_SIZE (15 bytes) are invalid
+ * even if the input buffer is long enough to hold them.
+ */
+ if (buf_len > MAX_INSN_SIZE)
+ buf_len = MAX_INSN_SIZE;
+
memset(insn, 0, sizeof(*insn));
insn->kaddr = kaddr;
insn->end_kaddr = kaddr + buf_len;