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 <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>
---
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
On 03/24/2017 03:58 AM, Pranith Kumar wrote: > 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 <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> > --- > target/i386/translate.c | 7 +++++++ > 1 file changed, 7 insertions(+) Reviewed-by: Richard Henderson <rth@twiddle.net> r~
Queued, thanks. Paolo On 23/03/2017 18:58, Pranith Kumar wrote: > 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 <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> > --- > 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. */ >
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