From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59892) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cr70j-0008WR-0l for qemu-devel@nongnu.org; Thu, 23 Mar 2017 13:58:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cr70f-0001r4-To for qemu-devel@nongnu.org; Thu, 23 Mar 2017 13:58:57 -0400 Received: from mail-yw0-x242.google.com ([2607:f8b0:4002:c05::242]:34846) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cr70f-0001qn-PO for qemu-devel@nongnu.org; Thu, 23 Mar 2017 13:58:53 -0400 Received: by mail-yw0-x242.google.com with SMTP id h11so24424803ywa.2 for ; Thu, 23 Mar 2017 10:58:53 -0700 (PDT) From: Pranith Kumar Date: Thu, 23 Mar 2017 13:58:51 -0400 Message-Id: <20170323175851.14342-1-bobby.prani@gmail.com> Subject: [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , Richard Henderson , Eduardo Habkost , "open list:All patches CC here" Cc: Peter Maydell Sending again since I messed by pbonzini's email. This fixes the bug: 'user-to-root privesc inside VM via bad translation caching' reported by Jann Horn here: https://bugs.chromium.org/p/project-zero/issues/detail?id=1122 CC: Richard Henderson CC: Peter Maydell CC: Paolo Bonzini Reported-by: Jann Horn Signed-off-by: Pranith Kumar --- target/i386/translate.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/target/i386/translate.c b/target/i386/translate.c index 72c1b03a2a..1d1372fb43 100644 --- a/target/i386/translate.c +++ b/target/i386/translate.c @@ -4418,6 +4418,13 @@ static target_ulong disas_insn(CPUX86State *env, DisasContext *s, s->vex_l = 0; s->vex_v = 0; next_byte: + /* x86 has an upper limit of 15 bytes for an instruction. Since we + * do not want to decode and generate IR for an illegal + * instruction, the following check limits the instruction size to + * 25 bytes: 14 prefix + 1 opc + 6 (modrm+sib+ofs) + 4 imm */ + if (s->pc - pc_start > 14) { + goto illegal_op; + } b = cpu_ldub_code(env, s->pc); s->pc++; /* Collect prefixes. */ -- 2.11.0