Commit 30663fd2 authored by Pranith Kumar's avatar Pranith Kumar Committed by Paolo Bonzini
Browse files

tcg/i386: Check the size of instruction being translated 

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



Reviewed-by: default avatarRichard Henderson <rth@twiddle.net>
CC: Peter Maydell <peter.maydell@linaro.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarPranith Kumar <bobby.prani@gmail.com>
Message-Id: <20170323175851.14342-1-bobby.prani@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 71407786

target/i386/translate.c

+7 −0
Original line number Diff line number Diff line
@@ -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.  */