[v8,08/11] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option
diff mbox series

Message ID 20200210150519.538333-9-gladkov.alexey@gmail.com
State New
Headers show
Series
  • proc: modernize proc to support multiple private instances
Related show

Commit Message

Alexey Gladkov Feb. 10, 2020, 3:05 p.m. UTC
If "hidepid=4" mount option is set then do not instantiate pids that
we can not ptrace. "hidepid=4" means that procfs should only contain
pids that the caller can ptrace.

Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Djalal Harouni <tixxdz@gmail.com>
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
---
 fs/proc/base.c          | 15 +++++++++++++++
 fs/proc/root.c          | 14 +++++++++++---
 include/linux/proc_fs.h |  1 +
 3 files changed, 27 insertions(+), 3 deletions(-)

Comments

Jordan Glover Feb. 10, 2020, 4:29 p.m. UTC | #1
On Monday, February 10, 2020 3:05 PM, Alexey Gladkov <gladkov.alexey@gmail.com> wrote:

> If "hidepid=4" mount option is set then do not instantiate pids that
> we can not ptrace. "hidepid=4" means that procfs should only contain
> pids that the caller can ptrace.
>
> Cc: Kees Cook keescook@chromium.org
> Cc: Andy Lutomirski luto@kernel.org
> Signed-off-by: Djalal Harouni tixxdz@gmail.com
> Signed-off-by: Alexey Gladkov gladkov.alexey@gmail.com
>
> fs/proc/base.c | 15 +++++++++++++++
> fs/proc/root.c | 14 +++++++++++---
> include/linux/proc_fs.h | 1 +
> 3 files changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 24b7c620ded3..49937d54e745 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -699,6 +699,14 @@ static bool has_pid_permissions(struct proc_fs_info *fs_info,
> struct task_struct *task,
> int hide_pid_min)
> {
>
> -   /*
> -   -   If 'hidpid' mount option is set force a ptrace check,
> -   -   we indicate that we are using a filesystem syscall
> -   -   by passing PTRACE_MODE_READ_FSCREDS
> -   */
> -   if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE)
> -         return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
>
>
> -   if (proc_fs_hide_pid(fs_info) < hide_pid_min)
>     return true;
>     if (in_group_p(proc_fs_pid_gid(fs_info)))
>     @@ -3271,7 +3279,14 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags)
>     if (!task)
>     goto out;
>
> -   /* Limit procfs to only ptracable tasks */
> -   if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE) {
> -         if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS))
>
>
> -         	goto out_put_task;
>
>
> -   }
> -   result = proc_pid_instantiate(dentry, task, NULL);
>     +out_put_task:
>     put_task_struct(task);
>     out:
>     return result;
>     diff --git a/fs/proc/root.c b/fs/proc/root.c
>     index e2bb015da1a8..5e27bb31f125 100644
>     --- a/fs/proc/root.c
>     +++ b/fs/proc/root.c
>     @@ -52,6 +52,15 @@ static const struct fs_parameter_description proc_fs_parameters = {
>     .specs = proc_param_specs,
>     };
>
>     +static inline int
>     +valid_hidepid(unsigned int value)
>     +{
>
> -   return (value == HIDEPID_OFF ||
> -         value == HIDEPID_NO_ACCESS ||
>
>
> -         value == HIDEPID_INVISIBLE ||
>
>
> -         value == HIDEPID_NOT_PTRACABLE);
>
>
>
> +}
> +
> static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
> {
> struct proc_fs_context *ctx = fc->fs_private;
> @@ -68,10 +77,9 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
> break;
>
> case Opt_hidepid:
>
> -         if (!valid_hidepid(result.uint_32))
>
>
> -         	return invalf(fc, "proc: unknown value of hidepid.\\n");
>           ctx->hidepid = result.uint_32;
>
>
>
> -         if (ctx->hidepid < HIDEPID_OFF ||
>
>
> -             ctx->hidepid > HIDEPID_INVISIBLE)
>
>
> -         	return invalf(fc, "proc: hidepid value must be between 0 and 2.\\n");
>           break;
>
>
>
> default:
> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> index f307940f8311..6822548405a7 100644
> --- a/include/linux/proc_fs.h
> +++ b/include/linux/proc_fs.h
> @@ -17,6 +17,7 @@ enum {
> HIDEPID_OFF = 0,
> HIDEPID_NO_ACCESS = 1,
> HIDEPID_INVISIBLE = 2,
>
> -   HIDEPID_NOT_PTRACABLE = 4, /* Limit pids to only ptracable pids */

Is there a reason new option is "4" instead of "3"? The order 1..2..4 may be
confusing for people.

Jordan
Alexey Gladkov Feb. 12, 2020, 2:34 p.m. UTC | #2
On Mon, Feb 10, 2020 at 04:29:31PM +0000, Jordan Glover wrote:
> On Monday, February 10, 2020 3:05 PM, Alexey Gladkov <gladkov.alexey@gmail.com> wrote:
> 
> > If "hidepid=4" mount option is set then do not instantiate pids that
> > we can not ptrace. "hidepid=4" means that procfs should only contain
> > pids that the caller can ptrace.
> >
> > Cc: Kees Cook keescook@chromium.org
> > Cc: Andy Lutomirski luto@kernel.org
> > Signed-off-by: Djalal Harouni tixxdz@gmail.com
> > Signed-off-by: Alexey Gladkov gladkov.alexey@gmail.com
> >
> > fs/proc/base.c | 15 +++++++++++++++
> > fs/proc/root.c | 14 +++++++++++---
> > include/linux/proc_fs.h | 1 +
> > 3 files changed, 27 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/proc/base.c b/fs/proc/base.c
> > index 24b7c620ded3..49937d54e745 100644
> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> > @@ -699,6 +699,14 @@ static bool has_pid_permissions(struct proc_fs_info *fs_info,
> > struct task_struct *task,
> > int hide_pid_min)
> > {
> >
> > -   /*
> > -   -   If 'hidpid' mount option is set force a ptrace check,
> > -   -   we indicate that we are using a filesystem syscall
> > -   -   by passing PTRACE_MODE_READ_FSCREDS
> > -   */
> > -   if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE)
> > -         return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
> >
> >
> > -   if (proc_fs_hide_pid(fs_info) < hide_pid_min)
> >     return true;
> >     if (in_group_p(proc_fs_pid_gid(fs_info)))
> >     @@ -3271,7 +3279,14 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags)
> >     if (!task)
> >     goto out;
> >
> > -   /* Limit procfs to only ptracable tasks */
> > -   if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE) {
> > -         if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS))
> >
> >
> > -         	goto out_put_task;
> >
> >
> > -   }
> > -   result = proc_pid_instantiate(dentry, task, NULL);
> >     +out_put_task:
> >     put_task_struct(task);
> >     out:
> >     return result;
> >     diff --git a/fs/proc/root.c b/fs/proc/root.c
> >     index e2bb015da1a8..5e27bb31f125 100644
> >     --- a/fs/proc/root.c
> >     +++ b/fs/proc/root.c
> >     @@ -52,6 +52,15 @@ static const struct fs_parameter_description proc_fs_parameters = {
> >     .specs = proc_param_specs,
> >     };
> >
> >     +static inline int
> >     +valid_hidepid(unsigned int value)
> >     +{
> >
> > -   return (value == HIDEPID_OFF ||
> > -         value == HIDEPID_NO_ACCESS ||
> >
> >
> > -         value == HIDEPID_INVISIBLE ||
> >
> >
> > -         value == HIDEPID_NOT_PTRACABLE);
> >
> >
> >
> > +}
> > +
> > static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
> > {
> > struct proc_fs_context *ctx = fc->fs_private;
> > @@ -68,10 +77,9 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
> > break;
> >
> > case Opt_hidepid:
> >
> > -         if (!valid_hidepid(result.uint_32))
> >
> >
> > -         	return invalf(fc, "proc: unknown value of hidepid.\\n");
> >           ctx->hidepid = result.uint_32;
> >
> >
> >
> > -         if (ctx->hidepid < HIDEPID_OFF ||
> >
> >
> > -             ctx->hidepid > HIDEPID_INVISIBLE)
> >
> >
> > -         	return invalf(fc, "proc: hidepid value must be between 0 and 2.\\n");
> >           break;
> >
> >
> >
> > default:
> > diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> > index f307940f8311..6822548405a7 100644
> > --- a/include/linux/proc_fs.h
> > +++ b/include/linux/proc_fs.h
> > @@ -17,6 +17,7 @@ enum {
> > HIDEPID_OFF = 0,
> > HIDEPID_NO_ACCESS = 1,
> > HIDEPID_INVISIBLE = 2,
> >
> > -   HIDEPID_NOT_PTRACABLE = 4, /* Limit pids to only ptracable pids */
> 
> Is there a reason new option is "4" instead of "3"? The order 1..2..4 may be
> confusing for people.

This is just mask. For now hidepid values are mutually exclusive, but
since it moved to uapi, I thought it would be good if there was an
opportunity to combine values.

Patch
diff mbox series

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 24b7c620ded3..49937d54e745 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -699,6 +699,14 @@  static bool has_pid_permissions(struct proc_fs_info *fs_info,
 				 struct task_struct *task,
 				 int hide_pid_min)
 {
+	/*
+	 * If 'hidpid' mount option is set force a ptrace check,
+	 * we indicate that we are using a filesystem syscall
+	 * by passing PTRACE_MODE_READ_FSCREDS
+	 */
+	if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE)
+		return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
+
 	if (proc_fs_hide_pid(fs_info) < hide_pid_min)
 		return true;
 	if (in_group_p(proc_fs_pid_gid(fs_info)))
@@ -3271,7 +3279,14 @@  struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags)
 	if (!task)
 		goto out;
 
+	/* Limit procfs to only ptracable tasks */
+	if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE) {
+		if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS))
+			goto out_put_task;
+	}
+
 	result = proc_pid_instantiate(dentry, task, NULL);
+out_put_task:
 	put_task_struct(task);
 out:
 	return result;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index e2bb015da1a8..5e27bb31f125 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -52,6 +52,15 @@  static const struct fs_parameter_description proc_fs_parameters = {
 	.specs		= proc_param_specs,
 };
 
+static inline int
+valid_hidepid(unsigned int value)
+{
+	return (value == HIDEPID_OFF ||
+		value == HIDEPID_NO_ACCESS ||
+		value == HIDEPID_INVISIBLE ||
+		value == HIDEPID_NOT_PTRACABLE);
+}
+
 static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
 {
 	struct proc_fs_context *ctx = fc->fs_private;
@@ -68,10 +77,9 @@  static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		break;
 
 	case Opt_hidepid:
+		if (!valid_hidepid(result.uint_32))
+			return invalf(fc, "proc: unknown value of hidepid.\n");
 		ctx->hidepid = result.uint_32;
-		if (ctx->hidepid < HIDEPID_OFF ||
-		    ctx->hidepid > HIDEPID_INVISIBLE)
-			return invalf(fc, "proc: hidepid value must be between 0 and 2.\n");
 		break;
 
 	default:
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index f307940f8311..6822548405a7 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -17,6 +17,7 @@  enum {
 	HIDEPID_OFF	  = 0,
 	HIDEPID_NO_ACCESS = 1,
 	HIDEPID_INVISIBLE = 2,
+	HIDEPID_NOT_PTRACABLE = 4, /* Limit pids to only ptracable pids */
 };
 
 struct proc_fs_info {