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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	"David S . Miller" <davem@davemloft.net>,
	Jon Medhurst <tixy@linaro.org>, Will Deacon <will.deacon@arm.com>,
	Arnd Bergmann <arnd@arndb.de>,
	David Howells <dhowells@redhat.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	"Tobin C . Harding" <me@tobin.cc>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Richter <tmricht@linux.ibm.com>,
	akpm@linux-foundation.org, acme@kernel.org, rostedt@goodmis.org,
	brueckner@linux.vnet.ibm.com, schwidefsky@de.ibm.com,
	stable@vger.kernel.org
Subject: Re: [PATCH v3 1/7] kprobes: Make blacklist root user read only
Date: Sat, 28 Apr 2018 00:58:31 +0900	[thread overview]
Message-ID: <20180428005831.d80829f93397984cd6899a6a@kernel.org> (raw)
In-Reply-To: <20180427070412.utb5e53zbnajcfv2@gmail.com>

On Fri, 27 Apr 2018 09:04:12 +0200
Ingo Molnar <mingo@kernel.org> wrote:

> 
> * Masami Hiramatsu <mhiramat@kernel.org> wrote:
> 
> > Since the blacklist file indicates a sensitive address
> > information to reader, it should be restricted to the
> > root user.
> > 
> > Suggested-by: Thomas Richter <tmricht@linux.ibm.com>
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> >  kernel/kprobes.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index ea619021d901..51096eece801 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -2621,7 +2621,7 @@ static int __init debugfs_kprobe_init(void)
> >  	if (!file)
> >  		goto error;
> >  
> > -	file = debugfs_create_file("blacklist", 0444, dir, NULL,
> > +	file = debugfs_create_file("blacklist", 0400, dir, NULL,
> >  				&debugfs_kprobe_blacklist_ops);
> >  	if (!file)
> >  		goto error;
> 
> Note that in a typical Linux distro debugfs is already root-only:
> 
>   fomalhaut:~> ls -ld /sys/kernel/debug
>   drwx------ 28 root root 0 Apr 23 08:55 /sys/kernel/debug
> 
> but this change might make sense if debugfs is mounted in some other fashion.
> 
> But the patch looks incomplete, 'blacklist' is not the only word-readable file in 
> the kprobes hierarchy. The kprobes directory itself, and the 'list' file is 
> readable as well:
> 
>   [root@fomalhaut ~]# ls -ld /sys/kernel/debug/kprobes
>   drwxr-xr-x 2 root root 0 Apr 23 08:55 /sys/kernel/debug/kprobes
> 
>   [root@fomalhaut ~]# ls -l /sys/kernel/debug/kprobes/
> 
>   -r--r--r-- 1 root root 0 Apr 23 08:55 blacklist
>   -rw------- 1 root root 0 Apr 23 08:55 enabled
>   -r--r--r-- 1 root root 0 Apr 23 08:55 list
> 
> So not just the blacklist should be 400 but 'list' as well, and the main kprobes 
> directory as well.

OK, I'll mark it 0400 too.
For the kprobes directory, as Thomas pointed in the original thread,
that is currently debugfs API's limitation.

https://patchwork.kernel.org/patch/10364817/

We only have debugfs_create_dir() but it doesn't have "mode" flag.

struct dentry *debugfs_create_dir(const char *name, struct dentry *parent);

And doesn't care the parent mode bits.

Thanks,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply	other threads:[~2018-04-27 15:58 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-27  6:39 [PATCH v3 0/7] kprobes: Fix %p in kprobes Masami Hiramatsu
2018-04-27  6:40 ` [PATCH v3 1/7] kprobes: Make blacklist root user read only Masami Hiramatsu
2018-04-27  6:56   ` Greg KH
2018-04-27 14:52     ` Masami Hiramatsu
2018-04-27  7:04   ` Ingo Molnar
2018-04-27 15:58     ` Masami Hiramatsu [this message]
2018-04-27  6:40 ` [PATCH v3 2/7] kprobes: Show blacklist addresses as same as kallsyms does Masami Hiramatsu
2018-04-27  7:14   ` Ingo Molnar
2018-04-27 16:10     ` Masami Hiramatsu
2018-04-27  6:41 ` [PATCH v3 3/7] kprobes: Show address of kprobes if " Masami Hiramatsu
2018-04-27  6:41 ` [PATCH v3 4/7] kprobes: Replace %p with other pointer types Masami Hiramatsu
2018-04-27  6:56   ` Ingo Molnar
2018-04-27 15:42     ` Masami Hiramatsu
2018-04-28  4:43       ` Masami Hiramatsu
2018-04-27  6:42 ` [PATCH v3 5/7] kprobes/x86: Fix %p uses in error messages Masami Hiramatsu
2018-04-27  6:58   ` Ingo Molnar
2018-04-27 15:06     ` Masami Hiramatsu
2018-04-27  6:42 ` [PATCH v3 6/7] kprobes/arm: " Masami Hiramatsu
2018-04-27  6:43 ` [PATCH v3 7/7] kprobes/arm64: " Masami Hiramatsu

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