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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: Richard Henderson <rth@twiddle.net>
CC: Peter Maydell <peter.maydell@linaro.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Message-Id: <20170323175851.14342-1-bobby.prani@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Pranith Kumar 2017-03-23 13:58:51 -04:00 committed by Paolo Bonzini
parent 7140778605
commit 30663fd26c
1 changed files with 7 additions and 0 deletions
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7
target/i386/translate.c
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@ -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. */