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* [PATCH v3 1/2] seccomp: hoist out filter resolving logic
@ 2017-10-11 15:39 Tycho Andersen
  2017-10-11 15:39 ` [PATCH v3 2/2] ptrace, seccomp: add support for retrieving seccomp metadata Tycho Andersen
  2017-11-28 23:42 ` [PATCH v3 1/2] seccomp: hoist out filter resolving logic Kees Cook
  0 siblings, 2 replies; 4+ messages in thread
From: Tycho Andersen @ 2017-10-11 15:39 UTC (permalink / raw)
  To: Kees Cook; +Cc: linux-kernel, Tycho Andersen, Andy Lutomirski, Oleg Nesterov

Hoist out the nth filter resolving logic that ptrace uses into a new
function. We'll use this in the next patch to implement the new
PTRACE_SECCOMP_GET_FILTER_FLAGS command.

v3: * significantly revamp get_nth_filter logic (Oleg)
    * rebase on 4.14-rc4, using the new __{get,put}_seccomp_filter
      primitives

Signed-off-by: Tycho Andersen <tycho@docker.com>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
---
 kernel/seccomp.c | 77 +++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 45 insertions(+), 32 deletions(-)

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index bb3a38005b9c..2e1568261ac4 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -977,49 +977,68 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
 }
 
 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
-long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
-			void __user *data)
+static struct seccomp_filter *get_nth_filter(struct task_struct *task,
+					     unsigned long filter_off)
 {
-	struct seccomp_filter *filter;
-	struct sock_fprog_kern *fprog;
-	long ret;
-	unsigned long count = 0;
-
-	if (!capable(CAP_SYS_ADMIN) ||
-	    current->seccomp.mode != SECCOMP_MODE_DISABLED) {
-		return -EACCES;
-	}
+	struct seccomp_filter *orig, *filter;
+	unsigned long count;
 
+	/*
+	 * Note: this is only correct because the caller should be the (ptrace)
+	 * tracer of the task, otherwise lock_task_sighand is needed.
+	 */
 	spin_lock_irq(&task->sighand->siglock);
+
 	if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
-		ret = -EINVAL;
-		goto out;
+		spin_unlock_irq(&task->sighand->siglock);
+		return ERR_PTR(-EINVAL);
 	}
 
-	filter = task->seccomp.filter;
-	while (filter) {
-		filter = filter->prev;
+	orig = task->seccomp.filter;
+	__get_seccomp_filter(orig);
+	spin_unlock_irq(&task->sighand->siglock);
+
+	count = 0;
+	for (filter = orig; filter; filter = filter->prev)
 		count++;
-	}
 
 	if (filter_off >= count) {
-		ret = -ENOENT;
+		filter = ERR_PTR(-ENOENT);
 		goto out;
 	}
-	count -= filter_off;
 
-	filter = task->seccomp.filter;
-	while (filter && count > 1) {
-		filter = filter->prev;
+	count -= filter_off;
+	for (filter = orig; filter && count > 1; filter = filter->prev)
 		count--;
-	}
 
 	if (WARN_ON(count != 1 || !filter)) {
-		/* The filter tree shouldn't shrink while we're using it. */
-		ret = -ENOENT;
+		filter = ERR_PTR(-ENOENT);
 		goto out;
 	}
 
+	__get_seccomp_filter(filter);
+
+out:
+	__put_seccomp_filter(orig);
+	return filter;
+}
+
+long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
+			void __user *data)
+{
+	struct seccomp_filter *filter;
+	struct sock_fprog_kern *fprog;
+	long ret;
+
+	if (!capable(CAP_SYS_ADMIN) ||
+	    current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+		return -EACCES;
+	}
+
+	filter = get_nth_filter(task, filter_off);
+	if (IS_ERR(filter))
+		return PTR_ERR(filter);
+
 	fprog = filter->prog->orig_prog;
 	if (!fprog) {
 		/* This must be a new non-cBPF filter, since we save
@@ -1034,17 +1053,11 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
 	if (!data)
 		goto out;
 
-	__get_seccomp_filter(filter);
-	spin_unlock_irq(&task->sighand->siglock);
-
 	if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
 		ret = -EFAULT;
 
-	__put_seccomp_filter(filter);
-	return ret;
-
 out:
-	spin_unlock_irq(&task->sighand->siglock);
+	__put_seccomp_filter(filter);
 	return ret;
 }
 #endif
-- 
2.11.0

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [PATCH v3 2/2] ptrace, seccomp: add support for retrieving seccomp metadata
  2017-10-11 15:39 [PATCH v3 1/2] seccomp: hoist out filter resolving logic Tycho Andersen
@ 2017-10-11 15:39 ` Tycho Andersen
  2017-11-28 23:42   ` Kees Cook
  2017-11-28 23:42 ` [PATCH v3 1/2] seccomp: hoist out filter resolving logic Kees Cook
  1 sibling, 1 reply; 4+ messages in thread
From: Tycho Andersen @ 2017-10-11 15:39 UTC (permalink / raw)
  To: Kees Cook; +Cc: linux-kernel, Tycho Andersen, Andy Lutomirski, Oleg Nesterov

With the new SECCOMP_FILTER_FLAG_LOG, we need to be able to extract these
flags for checkpoint restore, since they describe the state of a filter.

So, let's add PTRACE_SECCOMP_GET_METADATA, similar to ..._GET_FILTER, which
returns the metadata of the nth filter (right now, just the flags).
Hopefully this will be future proof, and new per-filter metadata can be
added to this struct.

v3: * use GET_METADATA instead of GET_FLAGS

Signed-off-by: Tycho Andersen <tycho@docker.com>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
---
 include/linux/seccomp.h     |  8 ++++++++
 include/uapi/linux/ptrace.h |  6 ++++++
 kernel/ptrace.c             |  4 ++++
 kernel/seccomp.c            | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 52 insertions(+)

diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index c8bef436b61d..a6dee99cd187 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -94,11 +94,19 @@ static inline void get_seccomp_filter(struct task_struct *tsk)
 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
 extern long seccomp_get_filter(struct task_struct *task,
 			       unsigned long filter_off, void __user *data);
+extern long seccomp_get_metadata(struct task_struct *task,
+				 unsigned long filter_off, void __user *data);
 #else
 static inline long seccomp_get_filter(struct task_struct *task,
 				      unsigned long n, void __user *data)
 {
 	return -EINVAL;
 }
+static inline long seccomp_get_metadata(struct task_struct *task,
+					unsigned long filter_off,
+					void __user *data)
+{
+	return -EINVAL;
+}
 #endif /* CONFIG_SECCOMP_FILTER && CONFIG_CHECKPOINT_RESTORE */
 #endif /* _LINUX_SECCOMP_H */
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index fb8106509000..4e9774812dba 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -65,6 +65,12 @@ struct ptrace_peeksiginfo_args {
 #define PTRACE_SETSIGMASK	0x420b
 
 #define PTRACE_SECCOMP_GET_FILTER	0x420c
+#define PTRACE_SECCOMP_GET_METADATA	0x420d
+
+struct seccomp_metadata {
+	unsigned long filter_off;	/* Input: which filter */
+	unsigned int flags;		/* Output: filter's flags */
+};
 
 /* Read signals from a shared (process wide) queue */
 #define PTRACE_PEEKSIGINFO_SHARED	(1 << 0)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 84b1367935e4..58291e9f3276 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1092,6 +1092,10 @@ int ptrace_request(struct task_struct *child, long request,
 		ret = seccomp_get_filter(child, addr, datavp);
 		break;
 
+	case PTRACE_SECCOMP_GET_METADATA:
+		ret = seccomp_get_metadata(child, addr, datavp);
+		break;
+
 	default:
 		break;
 	}
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 2e1568261ac4..ea762af4974d 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1060,6 +1060,40 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
 	__put_seccomp_filter(filter);
 	return ret;
 }
+
+long seccomp_get_metadata(struct task_struct *task,
+			  unsigned long size, void __user *data)
+{
+	long ret;
+	struct seccomp_filter *filter;
+	struct seccomp_metadata kmd = {};
+
+	if (!capable(CAP_SYS_ADMIN) ||
+	    current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+		return -EACCES;
+	}
+
+	size = min_t(unsigned long, size, sizeof(kmd));
+
+	if (copy_from_user(&kmd, data, size))
+		return -EFAULT;
+
+	filter = get_nth_filter(task, kmd.filter_off);
+	if (IS_ERR(filter))
+		return PTR_ERR(filter);
+
+	memset(&kmd, 0, sizeof(kmd));
+	if (filter->log)
+		kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
+
+	ret = size;
+	if (copy_to_user(data, &kmd, size))
+		ret = -EFAULT;
+
+	__put_seccomp_filter(filter);
+	return ret;
+
+}
 #endif
 
 #ifdef CONFIG_SYSCTL
-- 
2.11.0

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH v3 1/2] seccomp: hoist out filter resolving logic
  2017-10-11 15:39 [PATCH v3 1/2] seccomp: hoist out filter resolving logic Tycho Andersen
  2017-10-11 15:39 ` [PATCH v3 2/2] ptrace, seccomp: add support for retrieving seccomp metadata Tycho Andersen
@ 2017-11-28 23:42 ` Kees Cook
  1 sibling, 0 replies; 4+ messages in thread
From: Kees Cook @ 2017-11-28 23:42 UTC (permalink / raw)
  To: Tycho Andersen; +Cc: LKML, Andy Lutomirski, Oleg Nesterov

On Wed, Oct 11, 2017 at 8:39 AM, Tycho Andersen <tycho@docker.com> wrote:
> Hoist out the nth filter resolving logic that ptrace uses into a new
> function. We'll use this in the next patch to implement the new
> PTRACE_SECCOMP_GET_FILTER_FLAGS command.
>
> v3: * significantly revamp get_nth_filter logic (Oleg)
>     * rebase on 4.14-rc4, using the new __{get,put}_seccomp_filter
>       primitives
>
> Signed-off-by: Tycho Andersen <tycho@docker.com>
> CC: Kees Cook <keescook@chromium.org>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Oleg Nesterov <oleg@redhat.com>

Sorry for the giant delay in reviewing these. This all looks good,
thanks! Applying for -next.

-Kees

> ---
>  kernel/seccomp.c | 77 +++++++++++++++++++++++++++++++++-----------------------
>  1 file changed, 45 insertions(+), 32 deletions(-)
>
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index bb3a38005b9c..2e1568261ac4 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -977,49 +977,68 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
>  }
>
>  #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
> -long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
> -                       void __user *data)
> +static struct seccomp_filter *get_nth_filter(struct task_struct *task,
> +                                            unsigned long filter_off)
>  {
> -       struct seccomp_filter *filter;
> -       struct sock_fprog_kern *fprog;
> -       long ret;
> -       unsigned long count = 0;
> -
> -       if (!capable(CAP_SYS_ADMIN) ||
> -           current->seccomp.mode != SECCOMP_MODE_DISABLED) {
> -               return -EACCES;
> -       }
> +       struct seccomp_filter *orig, *filter;
> +       unsigned long count;
>
> +       /*
> +        * Note: this is only correct because the caller should be the (ptrace)
> +        * tracer of the task, otherwise lock_task_sighand is needed.
> +        */
>         spin_lock_irq(&task->sighand->siglock);
> +
>         if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
> -               ret = -EINVAL;
> -               goto out;
> +               spin_unlock_irq(&task->sighand->siglock);
> +               return ERR_PTR(-EINVAL);
>         }
>
> -       filter = task->seccomp.filter;
> -       while (filter) {
> -               filter = filter->prev;
> +       orig = task->seccomp.filter;
> +       __get_seccomp_filter(orig);
> +       spin_unlock_irq(&task->sighand->siglock);
> +
> +       count = 0;
> +       for (filter = orig; filter; filter = filter->prev)
>                 count++;
> -       }
>
>         if (filter_off >= count) {
> -               ret = -ENOENT;
> +               filter = ERR_PTR(-ENOENT);
>                 goto out;
>         }
> -       count -= filter_off;
>
> -       filter = task->seccomp.filter;
> -       while (filter && count > 1) {
> -               filter = filter->prev;
> +       count -= filter_off;
> +       for (filter = orig; filter && count > 1; filter = filter->prev)
>                 count--;
> -       }
>
>         if (WARN_ON(count != 1 || !filter)) {
> -               /* The filter tree shouldn't shrink while we're using it. */
> -               ret = -ENOENT;
> +               filter = ERR_PTR(-ENOENT);
>                 goto out;
>         }
>
> +       __get_seccomp_filter(filter);
> +
> +out:
> +       __put_seccomp_filter(orig);
> +       return filter;
> +}
> +
> +long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
> +                       void __user *data)
> +{
> +       struct seccomp_filter *filter;
> +       struct sock_fprog_kern *fprog;
> +       long ret;
> +
> +       if (!capable(CAP_SYS_ADMIN) ||
> +           current->seccomp.mode != SECCOMP_MODE_DISABLED) {
> +               return -EACCES;
> +       }
> +
> +       filter = get_nth_filter(task, filter_off);
> +       if (IS_ERR(filter))
> +               return PTR_ERR(filter);
> +
>         fprog = filter->prog->orig_prog;
>         if (!fprog) {
>                 /* This must be a new non-cBPF filter, since we save
> @@ -1034,17 +1053,11 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
>         if (!data)
>                 goto out;
>
> -       __get_seccomp_filter(filter);
> -       spin_unlock_irq(&task->sighand->siglock);
> -
>         if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
>                 ret = -EFAULT;
>
> -       __put_seccomp_filter(filter);
> -       return ret;
> -
>  out:
> -       spin_unlock_irq(&task->sighand->siglock);
> +       __put_seccomp_filter(filter);
>         return ret;
>  }
>  #endif
> --
> 2.11.0
>



-- 
Kees Cook
Pixel Security

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH v3 2/2] ptrace, seccomp: add support for retrieving seccomp metadata
  2017-10-11 15:39 ` [PATCH v3 2/2] ptrace, seccomp: add support for retrieving seccomp metadata Tycho Andersen
@ 2017-11-28 23:42   ` Kees Cook
  0 siblings, 0 replies; 4+ messages in thread
From: Kees Cook @ 2017-11-28 23:42 UTC (permalink / raw)
  To: Tycho Andersen; +Cc: LKML, Andy Lutomirski, Oleg Nesterov

On Wed, Oct 11, 2017 at 8:39 AM, Tycho Andersen <tycho@docker.com> wrote:
> With the new SECCOMP_FILTER_FLAG_LOG, we need to be able to extract these
> flags for checkpoint restore, since they describe the state of a filter.
>
> So, let's add PTRACE_SECCOMP_GET_METADATA, similar to ..._GET_FILTER, which
> returns the metadata of the nth filter (right now, just the flags).
> Hopefully this will be future proof, and new per-filter metadata can be
> added to this struct.
>
> v3: * use GET_METADATA instead of GET_FLAGS
>
> Signed-off-by: Tycho Andersen <tycho@docker.com>
> CC: Kees Cook <keescook@chromium.org>
> CC: Andy Lutomirski <luto@amacapital.net>
> CC: Oleg Nesterov <oleg@redhat.com>

Applied for -next (with a minor whitespace fix).

Thanks!

-Kees

> ---
>  include/linux/seccomp.h     |  8 ++++++++
>  include/uapi/linux/ptrace.h |  6 ++++++
>  kernel/ptrace.c             |  4 ++++
>  kernel/seccomp.c            | 34 ++++++++++++++++++++++++++++++++++
>  4 files changed, 52 insertions(+)
>
> diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
> index c8bef436b61d..a6dee99cd187 100644
> --- a/include/linux/seccomp.h
> +++ b/include/linux/seccomp.h
> @@ -94,11 +94,19 @@ static inline void get_seccomp_filter(struct task_struct *tsk)
>  #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
>  extern long seccomp_get_filter(struct task_struct *task,
>                                unsigned long filter_off, void __user *data);
> +extern long seccomp_get_metadata(struct task_struct *task,
> +                                unsigned long filter_off, void __user *data);
>  #else
>  static inline long seccomp_get_filter(struct task_struct *task,
>                                       unsigned long n, void __user *data)
>  {
>         return -EINVAL;
>  }
> +static inline long seccomp_get_metadata(struct task_struct *task,
> +                                       unsigned long filter_off,
> +                                       void __user *data)
> +{
> +       return -EINVAL;
> +}
>  #endif /* CONFIG_SECCOMP_FILTER && CONFIG_CHECKPOINT_RESTORE */
>  #endif /* _LINUX_SECCOMP_H */
> diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
> index fb8106509000..4e9774812dba 100644
> --- a/include/uapi/linux/ptrace.h
> +++ b/include/uapi/linux/ptrace.h
> @@ -65,6 +65,12 @@ struct ptrace_peeksiginfo_args {
>  #define PTRACE_SETSIGMASK      0x420b
>
>  #define PTRACE_SECCOMP_GET_FILTER      0x420c
> +#define PTRACE_SECCOMP_GET_METADATA    0x420d
> +
> +struct seccomp_metadata {
> +       unsigned long filter_off;       /* Input: which filter */
> +       unsigned int flags;             /* Output: filter's flags */
> +};
>
>  /* Read signals from a shared (process wide) queue */
>  #define PTRACE_PEEKSIGINFO_SHARED      (1 << 0)
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 84b1367935e4..58291e9f3276 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -1092,6 +1092,10 @@ int ptrace_request(struct task_struct *child, long request,
>                 ret = seccomp_get_filter(child, addr, datavp);
>                 break;
>
> +       case PTRACE_SECCOMP_GET_METADATA:
> +               ret = seccomp_get_metadata(child, addr, datavp);
> +               break;
> +
>         default:
>                 break;
>         }
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index 2e1568261ac4..ea762af4974d 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -1060,6 +1060,40 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
>         __put_seccomp_filter(filter);
>         return ret;
>  }
> +
> +long seccomp_get_metadata(struct task_struct *task,
> +                         unsigned long size, void __user *data)
> +{
> +       long ret;
> +       struct seccomp_filter *filter;
> +       struct seccomp_metadata kmd = {};
> +
> +       if (!capable(CAP_SYS_ADMIN) ||
> +           current->seccomp.mode != SECCOMP_MODE_DISABLED) {
> +               return -EACCES;
> +       }
> +
> +       size = min_t(unsigned long, size, sizeof(kmd));
> +
> +       if (copy_from_user(&kmd, data, size))
> +               return -EFAULT;
> +
> +       filter = get_nth_filter(task, kmd.filter_off);
> +       if (IS_ERR(filter))
> +               return PTR_ERR(filter);
> +
> +       memset(&kmd, 0, sizeof(kmd));
> +       if (filter->log)
> +               kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
> +
> +       ret = size;
> +       if (copy_to_user(data, &kmd, size))
> +               ret = -EFAULT;
> +
> +       __put_seccomp_filter(filter);
> +       return ret;
> +
> +}
>  #endif
>
>  #ifdef CONFIG_SYSCTL
> --
> 2.11.0
>



-- 
Kees Cook
Pixel Security

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-11-28 23:42 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2017-10-11 15:39 [PATCH v3 1/2] seccomp: hoist out filter resolving logic Tycho Andersen
2017-10-11 15:39 ` [PATCH v3 2/2] ptrace, seccomp: add support for retrieving seccomp metadata Tycho Andersen
2017-11-28 23:42   ` Kees Cook
2017-11-28 23:42 ` [PATCH v3 1/2] seccomp: hoist out filter resolving logic Kees Cook

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