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Peter Anvin" , x86@kernel.org, Ananth N Mavinakayanahalli , Anil S Keshavamurthy , "David S . Miller" , Jon Medhurst , Will Deacon , Arnd Bergmann , David Howells , Heiko Carstens , "Tobin C . Harding" , Linus Torvalds , Thomas Richter , 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 Message-Id: <20180428005831.d80829f93397984cd6899a6a@kernel.org> In-Reply-To: <20180427070412.utb5e53zbnajcfv2@gmail.com> References: <152481117776.22588.1210388093668905564.stgit@devbox> <152481120919.22588.16126591608892708741.stgit@devbox> <20180427070412.utb5e53zbnajcfv2@gmail.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri, 27 Apr 2018 09:04:12 +0200 Ingo Molnar wrote: > > * Masami Hiramatsu wrote: > > > Since the blacklist file indicates a sensitive address > > information to reader, it should be restricted to the > > root user. > > > > Suggested-by: Thomas Richter > > Signed-off-by: Masami Hiramatsu > > --- > > 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