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| author | Pranith Kumar <bobby.prani@gmail.com> | 2017-03-23 13:58:51 -0400 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2017-03-24 11:49:38 +0100 |
| commit | 30663fd26c0307e414622c7a8607fbc04f92ec14 (patch) | |
| tree | 68fdff3693c9c025e32cd01d03ca96274ecf90f1 | |
| parent | 71407786054cad26de7ef66718b2a57a4bcb49b5 (diff) | |
| download | focaccia-qemu-30663fd26c0307e414622c7a8607fbc04f92ec14.tar.gz focaccia-qemu-30663fd26c0307e414622c7a8607fbc04f92ec14.zip | |
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>
| -rw-r--r-- | target/i386/translate.c | 7 |
1 files changed, 7 insertions, 0 deletions
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. */ |