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From: Kees Cook <keescook@chromium.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Adam Zabrocki <pi3@pi3.com.pl>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org,
	"Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	"David S . Miller" <davem@davemloft.net>,
	Solar Designer <solar@openwall.com>
Subject: Re: [PATCH] x86/kprobes: Fix optprobe to detect padding int3 correctly
Date: Fri, 11 Dec 2020 11:39:15 -0800	[thread overview]
Message-ID: <202012111139.948F2ECF1@keescook> (raw)
In-Reply-To: <160767025681.3880685.16021570341428835411.stgit@devnote2>

On Fri, Dec 11, 2020 at 04:04:17PM +0900, Masami Hiramatsu wrote:
> Fix optprobe to detect padding int3 correctly.
> 
> Since commit 7705dc855797 ("x86/vmlinux: Use INT3 instead of NOP
> for linker fill bytes") changed the padding bytes between functions
> from nop to int3, when optprobe decodes a target function it finds
> int3 and gives up the jump optimization.
> 
> Instead of giving up any int3 detection, this checks whether the
> rest of bytes to the end of the function are int3 or not. If all
> of those are int3, those come from the linker. In that case,
> optprobe continues jump optimization.
> 
> Fixes: 7705dc855797 ("x86/vmlinux: Use INT3 instead of NOP for linker fill bytes")
> Cc: stable@vger.kernel.org
> Reported-by: Adam Zabrocki <pi3@pi3.com.pl>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

  parent reply	other threads:[~2020-12-11 21:10 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-11  7:04 Masami Hiramatsu
2020-12-11 14:49 ` Steven Rostedt
2020-12-11 19:39 ` Kees Cook [this message]
2020-12-11 20:04   ` Adam Zabrocki
2020-12-12 14:38 ` [tip: x86/urgent] x86/kprobes: Fix optprobe to detect INT3 padding correctly tip-bot2 for Masami Hiramatsu

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