linux-kernel - [PATCH 0/3] x86/insn: Fix not using prefixes.nbytes for loop over prefixes.bytes

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Message-Id: <160689905099.3084105.7880450206184269465.stgit@devnote2>
Date:   Wed,  2 Dec 2020 17:50:51 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Jann Horn <jannh@...gle.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/3] x86/insn: Fix not using prefixes.nbytes for loop over prefixes.bytes

Hi,

Here are the patches to fix the wrong loop boundary check
on insn.prefixes.bytes[] array.

Kees Cook reported that this issue that there are similar
wrong boundary check patterns in the x86 code.

Since the insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a same prefix is repeated, we have to
check whether the insn.prefixes.bytes[i] != 0 (*) and i < 4 instead
of insn.prefixes.nbytes.

(*) Note that insn.prefixes.bytes[] should be zeroed in insn_init()
before decoding, and 0x00 is not a legacy prefix. So if you see 0
on insn.prefix.bytes[], it indicates the end of the array. Or,
if the prefixes.bytes[] is filled with prefix bytes, we can check
the index is less than 4.

Thank you,

---

Masami Hiramatsu (3):
      x86/sev-es: Fix not using prefixes.nbytes for loop over prefixes.bytes
      x86/uprobes: Fix not using prefixes.nbytes for loop over prefixes.bytes
      x86/insn-eval: Fix not using prefixes.nbytes for loop over prefixes.bytes

 arch/x86/boot/compressed/sev-es.c |    2 +-
 arch/x86/kernel/uprobes.c         |    4 ++--
 arch/x86/lib/insn-eval.c          |    4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)

-- 
Masami Hiramatsu (Linaro) <mhiramat@...nel.org>