From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20449C43331 for ; Sat, 28 Mar 2020 20:28:52 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 470DB2071B for ; Sat, 28 Mar 2020 20:28:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="O356OkPU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 470DB2071B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18266-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 3591 invoked by uid 550); 28 Mar 2020 20:28:43 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 3568 invoked from network); 28 Mar 2020 20:28:42 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=MUiWV4pjfeHPi8U1e/rHhzPVFQ2nBZ/K1op0DmSl2ak=; b=O356OkPU3ESu244KOG9mhvpPy+52uafWy+esv/NqtJeU4HkZdS2FgU1+D6ku18Ey9U WwE1swFtAGXf6jIcipRl3rxt7eSXUxtW5jNPJbCl+RWJmyxlvMgSIRn/BFX3k8XEF5Jz fm+WSAuOQB8rXjlO7nq1GRvVm1DR6X/f6Bd1E= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=MUiWV4pjfeHPi8U1e/rHhzPVFQ2nBZ/K1op0DmSl2ak=; b=KmmkeJTgVZk0rxrsaDIWYD/VNSS23ckeX4rGw1fVcrhDU0GO+EgN4/ILoqyKVNmK9T Tuhveplxtd9piTNFW1DD2ggkmMJougveirv03wksAsIaBJebPO1nSMOr7s86kZUt9JmQ /CCbd9ODdACYaR5qr58gfSMNAf4VaYwk+6+y3y72SFpNvQZAq0gAJ4sW0GY4iSf8jOca utaY8nQfGhbFOU70JHNlsq50PRnwfPYs+tWHxazYMpPbSDAGGb9vSoADQG3fIbvPJLC7 okkmlDfNElBlyaaCt0eNPT7AGqKk7vwogefAf3LWhS4XqCMGTC8bWZCaxNV9KYk02kE6 azSw== X-Gm-Message-State: ANhLgQ0omivDGwTK4zgIFTlOI81Tc1LVC6YUS4ZvNM+d6vf7Xg1XUgU2 vELJp1IsD70LTeKUeWuVR7n4bg== X-Google-Smtp-Source: ADFU+vvfFxyZ2kTL+AiPQZIPrYo32pSmRxmE/hu6jvevOYpyed0FsDRABSVDRXjfu6Xe5G8kaOa63g== X-Received: by 2002:aa7:959a:: with SMTP id z26mr5695770pfj.211.1585427310147; Sat, 28 Mar 2020 13:28:30 -0700 (PDT) Date: Sat, 28 Mar 2020 13:28:28 -0700 From: Kees Cook To: Alexey Gladkov Cc: LKML , Kernel Hardening , Linux API , Linux FS Devel , Linux Security Module , Akinobu Mita , Alexander Viro , Alexey Dobriyan , Alexey Gladkov , Andrew Morton , Andy Lutomirski , Daniel Micay , Djalal Harouni , "Dmitry V . Levin" , "Eric W . Biederman" , Greg Kroah-Hartman , Ingo Molnar , "J . Bruce Fields" , Jeff Layton , Jonathan Corbet , Linus Torvalds , Oleg Nesterov Subject: Re: [PATCH v10 8/9] proc: use human-readable values for hidehid Message-ID: <202003281321.A69D9DE45@keescook> References: <20200327172331.418878-1-gladkov.alexey@gmail.com> <20200327172331.418878-9-gladkov.alexey@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200327172331.418878-9-gladkov.alexey@gmail.com> On Fri, Mar 27, 2020 at 06:23:30PM +0100, Alexey Gladkov wrote: > The hidepid parameter values are becoming more and more and it becomes > difficult to remember what each new magic number means. > > Suggested-by: Andy Lutomirski > Reviewed-by: Alexey Dobriyan > Signed-off-by: Alexey Gladkov > --- > Documentation/filesystems/proc.txt | 52 +++++++++++++++--------------- > fs/proc/inode.c | 13 +++++++- > fs/proc/root.c | 36 +++++++++++++++++++-- > 3 files changed, 71 insertions(+), 30 deletions(-) > > diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt > index bd0e0ab85048..af47672cb2cb 100644 > --- a/Documentation/filesystems/proc.txt > +++ b/Documentation/filesystems/proc.txt > @@ -2025,28 +2025,28 @@ The following mount options are supported: > gid= Set the group authorized to learn processes information. > subset= Show only the specified subset of procfs. > > -hidepid=0 means classic mode - everybody may access all /proc// directories > -(default). > - > -hidepid=1 means users may not access any /proc// directories but their > -own. Sensitive files like cmdline, sched*, status are now protected against > -other users. This makes it impossible to learn whether any user runs > -specific program (given the program doesn't reveal itself by its behaviour). > -As an additional bonus, as /proc//cmdline is unaccessible for other users, > -poorly written programs passing sensitive information via program arguments are > -now protected against local eavesdroppers. > - > -hidepid=2 means hidepid=1 plus all /proc// will be fully invisible to other > -users. It doesn't mean that it hides a fact whether a process with a specific > -pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), > -but it hides process' uid and gid, which may be learned by stat()'ing > -/proc// otherwise. It greatly complicates an intruder's task of gathering > -information about running processes, whether some daemon runs with elevated > -privileges, whether other user runs some sensitive program, whether other users > -run any program at all, etc. > - > -hidepid=4 means that procfs should only contain /proc// directories > -that the caller can ptrace. > +hidepid=off or hidepid=0 means classic mode - everybody may access all > +/proc// directories (default). > + > +hidepid=noaccess or hidepid=1 means users may not access any /proc// > +directories but their own. Sensitive files like cmdline, sched*, status are now > +protected against other users. This makes it impossible to learn whether any > +user runs specific program (given the program doesn't reveal itself by its > +behaviour). As an additional bonus, as /proc//cmdline is unaccessible for > +other users, poorly written programs passing sensitive information via program > +arguments are now protected against local eavesdroppers. > + > +hidepid=invisible or hidepid=2 means hidepid=noaccess plus all /proc// will > +be fully invisible to other users. It doesn't mean that it hides a fact whether > +a process with a specific pid value exists (it can be learned by other means, > +e.g. by "kill -0 $PID"), but it hides process' uid and gid, which may be learned > +by stat()'ing /proc// otherwise. It greatly complicates an intruder's task > +of gathering information about running processes, whether some daemon runs with > +elevated privileges, whether other user runs some sensitive program, whether > +other users run any program at all, etc. > + > +hidepid=ptraceable or hidepid=4 means that procfs should only contain > +/proc// directories that the caller can ptrace. > > gid= defines a group authorized to learn processes information otherwise > prohibited by hidepid=. If you use some daemon like identd which needs to learn > @@ -2093,8 +2093,8 @@ creates a new procfs instance. Mount options affect own procfs instance. > It means that it became possible to have several procfs instances > displaying tasks with different filtering options in one pid namespace. > > -# mount -o hidepid=2 -t proc proc /proc > -# mount -o hidepid=1 -t proc proc /tmp/proc > +# mount -o hidepid=invisible -t proc proc /proc > +# mount -o hidepid=noaccess -t proc proc /tmp/proc > # grep ^proc /proc/mounts > -proc /proc proc rw,relatime,hidepid=2 0 0 > -proc /tmp/proc proc rw,relatime,hidepid=1 0 0 > +proc /proc proc rw,relatime,hidepid=invisible 0 0 > +proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 > diff --git a/fs/proc/inode.c b/fs/proc/inode.c > index e6577ce6027b..f01fb4bed75c 100644 > --- a/fs/proc/inode.c > +++ b/fs/proc/inode.c > @@ -165,6 +165,17 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock > deactivate_super(old_sb); > } > > +static inline const char *hidepid2str(int v) > +{ > + switch (v) { > + case HIDEPID_OFF: return "off"; > + case HIDEPID_NO_ACCESS: return "noaccess"; > + case HIDEPID_INVISIBLE: return "invisible"; > + case HIDEPID_NOT_PTRACEABLE: return "ptraceable"; > + } > + BUG(); Please don't use BUG()[1]. Add a default case with a warn and return "unknown": switch (v) { case HIDEPID_OFF: return "off"; case HIDEPID_NO_ACCESS: return "noaccess"; case HIDEPID_INVISIBLE: return "invisible"; case HIDEPID_NOT_PTRACEABLE: return "ptraceable"; default: WARN_ON_ONCE("bad hide_pid value: %d\n", v); return "unknown"; } [1] https://lore.kernel.org/lkml/202003141524.59C619B51A@keescook/ > +} > + > static int proc_show_options(struct seq_file *seq, struct dentry *root) > { > struct proc_fs_info *fs_info = proc_sb_info(root->d_sb); > @@ -172,7 +183,7 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root) > if (!gid_eq(fs_info->pid_gid, GLOBAL_ROOT_GID)) > seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid)); > if (fs_info->hide_pid != HIDEPID_OFF) > - seq_printf(seq, ",hidepid=%u", fs_info->hide_pid); > + seq_printf(seq, ",hidepid=%s", hidepid2str(fs_info->hide_pid)); > if (fs_info->pidonly != PROC_PIDONLY_OFF) > seq_printf(seq, ",subset=pid"); > > diff --git a/fs/proc/root.c b/fs/proc/root.c > index dbcd96f07c7a..ba782d6e6197 100644 > --- a/fs/proc/root.c > +++ b/fs/proc/root.c > @@ -45,7 +45,7 @@ enum proc_param { > > static const struct fs_parameter_spec proc_fs_parameters[] = { > fsparam_u32("gid", Opt_gid), > - fsparam_u32("hidepid", Opt_hidepid), > + fsparam_string("hidepid", Opt_hidepid), > fsparam_string("subset", Opt_subset), > {} > }; > @@ -58,6 +58,35 @@ static inline int valid_hidepid(unsigned int value) > value == HIDEPID_NOT_PTRACEABLE); > } > > +static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param) > +{ > + struct proc_fs_context *ctx = fc->fs_private; > + struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid); > + struct fs_parse_result result; > + int base = (unsigned long)hidepid_u32_spec.data; > + > + if (param->type != fs_value_is_string) > + return invalf(fc, "proc: unexpected type of hidepid value\n"); > + > + if (!kstrtouint(param->string, base, &result.uint_32)) { > + ctx->hidepid = result.uint_32; This need to bounds-check the value with a call to valid_hidepid(), yes? > + return 0; > + } > + > + if (!strcmp(param->string, "off")) > + ctx->hidepid = HIDEPID_OFF; > + else if (!strcmp(param->string, "noaccess")) > + ctx->hidepid = HIDEPID_NO_ACCESS; > + else if (!strcmp(param->string, "invisible")) > + ctx->hidepid = HIDEPID_INVISIBLE; > + else if (!strcmp(param->string, "ptraceable")) > + ctx->hidepid = HIDEPID_NOT_PTRACEABLE; > + else > + return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string); > + > + return 0; > +} > + > static int proc_parse_subset_param(struct fs_context *fc, char *value) > { > struct proc_fs_context *ctx = fc->fs_private; > @@ -97,9 +126,10 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) > break; > > case Opt_hidepid: > - if (!valid_hidepid(result.uint_32)) > + if (proc_parse_hidepid_param(fc, param)) > + return -EINVAL; > + if (!valid_hidepid(ctx->hidepid)) > return invalf(fc, "proc: unknown value of hidepid.\n"); > - ctx->hidepid = result.uint_32; > break; > > case Opt_subset: > -- > 2.25.2 > -- Kees Cook