* [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated
@ 2017-03-23 17:58 Pranith Kumar
2017-03-23 21:13 ` Richard Henderson
2017-03-24 10:49 ` Paolo Bonzini
0 siblings, 2 replies; 4+ messages in thread
From: Pranith Kumar @ 2017-03-23 17:58 UTC (permalink / raw)
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 <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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated
2017-03-23 17:58 [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated Pranith Kumar
@ 2017-03-23 21:13 ` Richard Henderson
2017-03-24 10:49 ` Paolo Bonzini
1 sibling, 0 replies; 4+ messages in thread
From: Richard Henderson @ 2017-03-23 21:13 UTC (permalink / raw)
To: Pranith Kumar, Paolo Bonzini, Eduardo Habkost,
open list:All patches CC here
Cc: Peter Maydell
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~
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated
2017-03-23 17:58 [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated Pranith Kumar
2017-03-23 21:13 ` Richard Henderson
@ 2017-03-24 10:49 ` Paolo Bonzini
1 sibling, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2017-03-24 10:49 UTC (permalink / raw)
To: Pranith Kumar, Richard Henderson, Eduardo Habkost,
open list:All patches CC here
Cc: Peter Maydell
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. */
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated
@ 2017-03-23 17:57 Pranith Kumar
0 siblings, 0 replies; 4+ messages in thread
From: Pranith Kumar @ 2017-03-23 17:57 UTC (permalink / raw)
To: Paolo Bonzini, Richard Henderson, Eduardo Habkost,
open list:All patches CC here
Cc: Peter Maydell, Paolo Bonzini
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 <paolo.bonzini@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
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-03-24 10:50 UTC | newest]
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2017-03-23 17:58 [Qemu-devel] [PATCH] tcg/i386: Check the size of instruction being translated Pranith Kumar
2017-03-23 21:13 ` Richard Henderson
2017-03-24 10:49 ` Paolo Bonzini
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2017-03-23 17:57 Pranith Kumar
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