linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>, Adam Zabrocki <pi3@pi3.com.pl>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Kees Cook <keescook@chromium.org>,
	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 09:49:50 -0500	[thread overview]
Message-ID: <20201211094950.6c3f040d@gandalf.local.home> (raw)
In-Reply-To: <160767025681.3880685.16021570341428835411.stgit@devnote2>

On Fri, 11 Dec 2020 16:04:17 +0900
Masami Hiramatsu <mhiramat@kernel.org> 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: Steven Rostedt (VMware) <rostedt@goodmis.org>

This should probably go in via tip.

-- Steve


> ---
>  arch/x86/kernel/kprobes/opt.c |   22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
> index 041f0b50bc27..b5cf39f1a855 100644
> --- a/arch/x86/kernel/kprobes/opt.c
> +++ b/arch/x86/kernel/kprobes/opt.c
> @@ -272,6 +272,19 @@ static int insn_is_indirect_jump(struct insn *insn)
>  	return ret;
>  }
>  
> +static bool is_padding_int3(unsigned long addr, unsigned long eaddr)
> +{
> +	unsigned char ops;
> +
> +	for (; addr < eaddr; addr++) {
> +		if (get_kernel_nofault(ops, (void *)addr) < 0 ||
> +		    ops != INT3_INSN_OPCODE)
> +			return false;
> +	}
> +
> +	return true;
> +}
> +
>  /* Decode whole function to ensure any instructions don't jump into target */
>  static int can_optimize(unsigned long paddr)
>  {
> @@ -310,9 +323,14 @@ static int can_optimize(unsigned long paddr)
>  			return 0;
>  		kernel_insn_init(&insn, (void *)recovered_insn, MAX_INSN_SIZE);
>  		insn_get_length(&insn);
> -		/* Another subsystem puts a breakpoint */
> +		/*
> +		 * In the case of detecting unknown breakpoint, this could be
> +		 * a padding int3 between functions. Let's check that all the
> +		 * rest of the bytes are also int3.
> +		 */
>  		if (insn.opcode.bytes[0] == INT3_INSN_OPCODE)
> -			return 0;
> +			return is_padding_int3(addr, paddr - offset + size) ? 1 : 0;
> +
>  		/* Recover address */
>  		insn.kaddr = (void *)addr;
>  		insn.next_byte = (void *)(addr + insn.length);


  reply	other threads:[~2020-12-11 15:31 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 [this message]
2020-12-11 19:39 ` Kees Cook
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201211094950.6c3f040d@gandalf.local.home \
    --to=rostedt@goodmis.org \
    --cc=anil.s.keshavamurthy@intel.com \
    --cc=bp@alien8.de \
    --cc=davem@davemloft.net \
    --cc=hpa@zytor.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mhiramat@kernel.org \
    --cc=mingo@kernel.org \
    --cc=mingo@redhat.com \
    --cc=naveen.n.rao@linux.ibm.com \
    --cc=pi3@pi3.com.pl \
    --cc=solar@openwall.com \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH] x86/kprobes: Fix optprobe to detect padding int3 correctly' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox