qemu-devel.nongnu.org archive mirror
 help / color / mirror / Atom feed
* [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
* [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]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
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
  -- strict thread matches above, loose matches on Subject: below --
2017-03-23 17:57 Pranith Kumar

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).