[RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF)

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* [RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF)
@ 2012-09-20 23:37 ` Kees Cook
  0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2012-09-20 23:37 UTC (permalink / raw)
  To: Michael Kerrisk; +Cc: linux-man, linux-doc, linux-kernel, wad

This adds a short summary of the arguments used for "mode 2" (BPF)
seccomp.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 man2/prctl.2 |   40 ++++++++++++++++++++++++++++++----------
 1 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/man2/prctl.2 b/man2/prctl.2
index eb53aa8..a44aa32 100644
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -41,11 +41,12 @@
 .\" 2012-04 Cyrill Gorcunov, Document PR_SET_MM
 .\" 2012-04-25 Michael Kerrisk, Document PR_TASK_PERF_EVENTS_DISABLE and
 .\"				PR_TASK_PERF_EVENTS_ENABLE
+.\" 2012-09-20 Kees Cook, update PR_SET_SECCOMP for mode 2
 .\"
 .\" FIXME: Document PR_SET_TIMERSLACK and PR_GET_TIMERSLACK (new in 2.6.28)
 .\"		commit 6976675d94042fbd446231d1bd8b7de71a980ada
 .\"
-.TH PRCTL 2 2012-04-23 "Linux" "Linux Programmer's Manual"
+.TH PRCTL 2 2012-09-20 "Linux" "Linux Programmer's Manual"
 .SH NAME
 prctl \- operations on a process
 .SH SYNOPSIS
@@ -235,11 +236,17 @@ in the location pointed to by
 .\" See http://thread.gmane.org/gmane.linux.kernel/542632
 .\" [PATCH 0 of 2] seccomp updates
 .\" andrea@cpushare.com
-Set the secure computing mode for the calling thread.
-In the current implementation,
+Set the secure computing mode for the calling thread, to limit
+the available syscalls.
+The seccomp mode is selected via
+.IR arg2 .
+(The seccomp constants are defined in
+.IR <linux/seccomp.h> .)
+
+With
 .IR arg2
-must be 1.
-After the secure computing mode has been set to 1,
+set to
+.BR SECCOMP_MODE_STRICT
 the only system calls that the thread is permitted to make are
 .BR read (2),
 .BR write (2),
@@ -249,22 +256,35 @@ and
 Other system calls result in the delivery of a
 .BR SIGKILL
 signal.
-Secure computing mode is useful for number-crunching applications
+Strict secure computing mode is useful for number-crunching applications
 that may need to execute untrusted byte code,
 perhaps obtained by reading from a pipe or socket.
 This operation is only available
 if the kernel is configured with CONFIG_SECCOMP enabled.
+
+With
+.IR arg2
+set to
+.BR SECCOMP_MODE_FILTER " (since Linux 3.5)"
+the system calls allowed are
+defined by a pointer passed in
+.IR arg3
+to a Berkeley Packet Filter, which can be designed to filter
+arbitrary syscalls and syscall arguments.
+This mode is only available if the kernel is configured with
+CONFIG_SECCOMP_FILTER enabled.
+
 .TP
 .BR PR_GET_SECCOMP " (since Linux 2.6.23)"
 Return the secure computing mode of the calling thread.
-Not very useful for the current implementation (mode equals 1),
-but may be useful for other possible future modes:
-if the caller is not in secure computing mode, this operation returns 0;
-if the caller is in secure computing mode, then the
+If the caller is not in secure computing mode, this operation returns 0;
+if the caller is in strict secure computing mode, then the
 .BR prctl ()
 call will cause a
 .B SIGKILL
 signal to be sent to the process.
+If the caller is in filter mode, and this syscall is allowed by the
+seccomp filters, it returns 2.
 This operation is only available
 if the kernel is configured with CONFIG_SECCOMP enabled.
 .TP
-- 
1.7.0.4

-- 
Kees Cook
Chrome OS Security

^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF)
@ 2012-09-20 23:37 ` Kees Cook
  0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2012-09-20 23:37 UTC (permalink / raw)
  To: Michael Kerrisk
  Cc: linux-man-u79uwXL29TY76Z2rM5mHXA,
	linux-doc-u79uwXL29TY76Z2rM5mHXA,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA, wad-F7+t8E8rja9g9hUCZPvPmw

This adds a short summary of the arguments used for "mode 2" (BPF)
seccomp.

Signed-off-by: Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
---
 man2/prctl.2 |   40 ++++++++++++++++++++++++++++++----------
 1 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/man2/prctl.2 b/man2/prctl.2
index eb53aa8..a44aa32 100644
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -41,11 +41,12 @@
 .\" 2012-04 Cyrill Gorcunov, Document PR_SET_MM
 .\" 2012-04-25 Michael Kerrisk, Document PR_TASK_PERF_EVENTS_DISABLE and
 .\"				PR_TASK_PERF_EVENTS_ENABLE
+.\" 2012-09-20 Kees Cook, update PR_SET_SECCOMP for mode 2
 .\"
 .\" FIXME: Document PR_SET_TIMERSLACK and PR_GET_TIMERSLACK (new in 2.6.28)
 .\"		commit 6976675d94042fbd446231d1bd8b7de71a980ada
 .\"
-.TH PRCTL 2 2012-04-23 "Linux" "Linux Programmer's Manual"
+.TH PRCTL 2 2012-09-20 "Linux" "Linux Programmer's Manual"
 .SH NAME
 prctl \- operations on a process
 .SH SYNOPSIS
@@ -235,11 +236,17 @@ in the location pointed to by
 .\" See http://thread.gmane.org/gmane.linux.kernel/542632
 .\" [PATCH 0 of 2] seccomp updates
 .\" andrea-Vyt77T80VFVWk0Htik3J/w@public.gmane.org
-Set the secure computing mode for the calling thread.
-In the current implementation,
+Set the secure computing mode for the calling thread, to limit
+the available syscalls.
+The seccomp mode is selected via
+.IR arg2 .
+(The seccomp constants are defined in
+.IR <linux/seccomp.h> .)
+
+With
 .IR arg2
-must be 1.
-After the secure computing mode has been set to 1,
+set to
+.BR SECCOMP_MODE_STRICT
 the only system calls that the thread is permitted to make are
 .BR read (2),
 .BR write (2),
@@ -249,22 +256,35 @@ and
 Other system calls result in the delivery of a
 .BR SIGKILL
 signal.
-Secure computing mode is useful for number-crunching applications
+Strict secure computing mode is useful for number-crunching applications
 that may need to execute untrusted byte code,
 perhaps obtained by reading from a pipe or socket.
 This operation is only available
 if the kernel is configured with CONFIG_SECCOMP enabled.
+
+With
+.IR arg2
+set to
+.BR SECCOMP_MODE_FILTER " (since Linux 3.5)"
+the system calls allowed are
+defined by a pointer passed in
+.IR arg3
+to a Berkeley Packet Filter, which can be designed to filter
+arbitrary syscalls and syscall arguments.
+This mode is only available if the kernel is configured with
+CONFIG_SECCOMP_FILTER enabled.
+
 .TP
 .BR PR_GET_SECCOMP " (since Linux 2.6.23)"
 Return the secure computing mode of the calling thread.
-Not very useful for the current implementation (mode equals 1),
-but may be useful for other possible future modes:
-if the caller is not in secure computing mode, this operation returns 0;
-if the caller is in secure computing mode, then the
+If the caller is not in secure computing mode, this operation returns 0;
+if the caller is in strict secure computing mode, then the
 .BR prctl ()
 call will cause a
 .B SIGKILL
 signal to be sent to the process.
+If the caller is in filter mode, and this syscall is allowed by the
+seccomp filters, it returns 2.
 This operation is only available
 if the kernel is configured with CONFIG_SECCOMP enabled.
 .TP
-- 
1.7.0.4

-- 
Kees Cook
Chrome OS Security
--
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^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF)
  2012-09-20 23:37 ` Kees Cook
  (?)
@ 2012-10-22  4:56 ` Michael Kerrisk (man-pages)
  2012-10-22  7:34   ` Michael Kerrisk (man-pages)
  -1 siblings, 1 reply; 6+ messages in thread
From: Michael Kerrisk (man-pages) @ 2012-10-22  4:56 UTC (permalink / raw)
  To: Kees Cook; +Cc: linux-man, linux-doc, linux-kernel, wad

Hello Kees,

On Fri, Sep 21, 2012 at 1:37 AM, Kees Cook <keescook@chromium.org> wrote:
> This adds a short summary of the arguments used for "mode 2" (BPF)
> seccomp.

Thanks very much. Applied.

Cheers,

Michael


> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  man2/prctl.2 |   40 ++++++++++++++++++++++++++++++----------
>  1 files changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/man2/prctl.2 b/man2/prctl.2
> index eb53aa8..a44aa32 100644
> --- a/man2/prctl.2
> +++ b/man2/prctl.2
> @@ -41,11 +41,12 @@
>  .\" 2012-04 Cyrill Gorcunov, Document PR_SET_MM
>  .\" 2012-04-25 Michael Kerrisk, Document PR_TASK_PERF_EVENTS_DISABLE and
>  .\"                            PR_TASK_PERF_EVENTS_ENABLE
> +.\" 2012-09-20 Kees Cook, update PR_SET_SECCOMP for mode 2
>  .\"
>  .\" FIXME: Document PR_SET_TIMERSLACK and PR_GET_TIMERSLACK (new in 2.6.28)
>  .\"            commit 6976675d94042fbd446231d1bd8b7de71a980ada
>  .\"
> -.TH PRCTL 2 2012-04-23 "Linux" "Linux Programmer's Manual"
> +.TH PRCTL 2 2012-09-20 "Linux" "Linux Programmer's Manual"
>  .SH NAME
>  prctl \- operations on a process
>  .SH SYNOPSIS
> @@ -235,11 +236,17 @@ in the location pointed to by
>  .\" See http://thread.gmane.org/gmane.linux.kernel/542632
>  .\" [PATCH 0 of 2] seccomp updates
>  .\" andrea@cpushare.com
> -Set the secure computing mode for the calling thread.
> -In the current implementation,
> +Set the secure computing mode for the calling thread, to limit
> +the available syscalls.
> +The seccomp mode is selected via
> +.IR arg2 .
> +(The seccomp constants are defined in
> +.IR <linux/seccomp.h> .)
> +
> +With
>  .IR arg2
> -must be 1.
> -After the secure computing mode has been set to 1,
> +set to
> +.BR SECCOMP_MODE_STRICT
>  the only system calls that the thread is permitted to make are
>  .BR read (2),
>  .BR write (2),
> @@ -249,22 +256,35 @@ and
>  Other system calls result in the delivery of a
>  .BR SIGKILL
>  signal.
> -Secure computing mode is useful for number-crunching applications
> +Strict secure computing mode is useful for number-crunching applications
>  that may need to execute untrusted byte code,
>  perhaps obtained by reading from a pipe or socket.
>  This operation is only available
>  if the kernel is configured with CONFIG_SECCOMP enabled.
> +
> +With
> +.IR arg2
> +set to
> +.BR SECCOMP_MODE_FILTER " (since Linux 3.5)"
> +the system calls allowed are
> +defined by a pointer passed in
> +.IR arg3
> +to a Berkeley Packet Filter, which can be designed to filter
> +arbitrary syscalls and syscall arguments.
> +This mode is only available if the kernel is configured with
> +CONFIG_SECCOMP_FILTER enabled.
> +
>  .TP
>  .BR PR_GET_SECCOMP " (since Linux 2.6.23)"
>  Return the secure computing mode of the calling thread.
> -Not very useful for the current implementation (mode equals 1),
> -but may be useful for other possible future modes:
> -if the caller is not in secure computing mode, this operation returns 0;
> -if the caller is in secure computing mode, then the
> +If the caller is not in secure computing mode, this operation returns 0;
> +if the caller is in strict secure computing mode, then the
>  .BR prctl ()
>  call will cause a
>  .B SIGKILL
>  signal to be sent to the process.
> +If the caller is in filter mode, and this syscall is allowed by the
> +seccomp filters, it returns 2.
>  This operation is only available
>  if the kernel is configured with CONFIG_SECCOMP enabled.
>  .TP
> --
> 1.7.0.4
>
> --
> Kees Cook
> Chrome OS Security



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF)
  2012-10-22  4:56 ` Michael Kerrisk (man-pages)
@ 2012-10-22  7:34   ` Michael Kerrisk (man-pages)
  2012-10-22 15:15     ` Kees Cook
  0 siblings, 1 reply; 6+ messages in thread
From: Michael Kerrisk (man-pages) @ 2012-10-22  7:34 UTC (permalink / raw)
  To: Kees Cook; +Cc: linux-man, linux-doc, linux-kernel, wad, Michael Kerrisk

Kees,

A couple of questions about SECCOMP_MODE_FILTER.

I added some words that the arg3 is a pointer to 'struct fprog'. Can
you confirmn that's correct?

If the CONFIG_SECCOMP_FILTER permits fork(), is the seccomp setting
inherited across fork()? Similar question for execve().

Thanks,

Michael

On Mon, Oct 22, 2012 at 6:56 AM, Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
> Hello Kees,
>
> On Fri, Sep 21, 2012 at 1:37 AM, Kees Cook <keescook@chromium.org> wrote:
>> This adds a short summary of the arguments used for "mode 2" (BPF)
>> seccomp.
>
> Thanks very much. Applied.
>
> Cheers,
>
> Michael
>
>
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>>  man2/prctl.2 |   40 ++++++++++++++++++++++++++++++----------
>>  1 files changed, 30 insertions(+), 10 deletions(-)
>>
>> diff --git a/man2/prctl.2 b/man2/prctl.2
>> index eb53aa8..a44aa32 100644
>> --- a/man2/prctl.2
>> +++ b/man2/prctl.2
>> @@ -41,11 +41,12 @@
>>  .\" 2012-04 Cyrill Gorcunov, Document PR_SET_MM
>>  .\" 2012-04-25 Michael Kerrisk, Document PR_TASK_PERF_EVENTS_DISABLE and
>>  .\"                            PR_TASK_PERF_EVENTS_ENABLE
>> +.\" 2012-09-20 Kees Cook, update PR_SET_SECCOMP for mode 2
>>  .\"
>>  .\" FIXME: Document PR_SET_TIMERSLACK and PR_GET_TIMERSLACK (new in 2.6.28)
>>  .\"            commit 6976675d94042fbd446231d1bd8b7de71a980ada
>>  .\"
>> -.TH PRCTL 2 2012-04-23 "Linux" "Linux Programmer's Manual"
>> +.TH PRCTL 2 2012-09-20 "Linux" "Linux Programmer's Manual"
>>  .SH NAME
>>  prctl \- operations on a process
>>  .SH SYNOPSIS
>> @@ -235,11 +236,17 @@ in the location pointed to by
>>  .\" See http://thread.gmane.org/gmane.linux.kernel/542632
>>  .\" [PATCH 0 of 2] seccomp updates
>>  .\" andrea@cpushare.com
>> -Set the secure computing mode for the calling thread.
>> -In the current implementation,
>> +Set the secure computing mode for the calling thread, to limit
>> +the available syscalls.
>> +The seccomp mode is selected via
>> +.IR arg2 .
>> +(The seccomp constants are defined in
>> +.IR <linux/seccomp.h> .)
>> +
>> +With
>>  .IR arg2
>> -must be 1.
>> -After the secure computing mode has been set to 1,
>> +set to
>> +.BR SECCOMP_MODE_STRICT
>>  the only system calls that the thread is permitted to make are
>>  .BR read (2),
>>  .BR write (2),
>> @@ -249,22 +256,35 @@ and
>>  Other system calls result in the delivery of a
>>  .BR SIGKILL
>>  signal.
>> -Secure computing mode is useful for number-crunching applications
>> +Strict secure computing mode is useful for number-crunching applications
>>  that may need to execute untrusted byte code,
>>  perhaps obtained by reading from a pipe or socket.
>>  This operation is only available
>>  if the kernel is configured with CONFIG_SECCOMP enabled.
>> +
>> +With
>> +.IR arg2
>> +set to
>> +.BR SECCOMP_MODE_FILTER " (since Linux 3.5)"
>> +the system calls allowed are
>> +defined by a pointer passed in
>> +.IR arg3
>> +to a Berkeley Packet Filter, which can be designed to filter
>> +arbitrary syscalls and syscall arguments.
>> +This mode is only available if the kernel is configured with
>> +CONFIG_SECCOMP_FILTER enabled.
>> +
>>  .TP
>>  .BR PR_GET_SECCOMP " (since Linux 2.6.23)"
>>  Return the secure computing mode of the calling thread.
>> -Not very useful for the current implementation (mode equals 1),
>> -but may be useful for other possible future modes:
>> -if the caller is not in secure computing mode, this operation returns 0;
>> -if the caller is in secure computing mode, then the
>> +If the caller is not in secure computing mode, this operation returns 0;
>> +if the caller is in strict secure computing mode, then the
>>  .BR prctl ()
>>  call will cause a
>>  .B SIGKILL
>>  signal to be sent to the process.
>> +If the caller is in filter mode, and this syscall is allowed by the
>> +seccomp filters, it returns 2.
>>  This operation is only available
>>  if the kernel is configured with CONFIG_SECCOMP enabled.
>>  .TP
>> --
>> 1.7.0.4
>>
>> --
>> Kees Cook
>> Chrome OS Security
>
>
>
> --
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Author of "The Linux Programming Interface"; http://man7.org/tlpi/



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF)
  2012-10-22  7:34   ` Michael Kerrisk (man-pages)
@ 2012-10-22 15:15     ` Kees Cook
  2012-10-22 21:43       ` Michael Kerrisk (man-pages)
  0 siblings, 1 reply; 6+ messages in thread
From: Kees Cook @ 2012-10-22 15:15 UTC (permalink / raw)
  To: mtk.manpages; +Cc: linux-man, linux-doc, linux-kernel, wad

On Mon, Oct 22, 2012 at 12:34 AM, Michael Kerrisk (man-pages)
<mtk.manpages@gmail.com> wrote:
> Kees,
>
> A couple of questions about SECCOMP_MODE_FILTER.
>
> I added some words that the arg3 is a pointer to 'struct fprog'. Can
> you confirmn that's correct?

Correct. Good idea to add this detail.

> If the CONFIG_SECCOMP_FILTER permits fork(), is the seccomp setting
> inherited across fork()? Similar question for execve().

Yes for both. Additionally, the filters are cumulative. (If the
filters allows prctl, additional filters can be appended; they are run
in order until the first non-allow result is seen.)

-Kees

-- 
Kees Cook
Chrome OS Security

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF)
  2012-10-22 15:15     ` Kees Cook
@ 2012-10-22 21:43       ` Michael Kerrisk (man-pages)
  0 siblings, 0 replies; 6+ messages in thread
From: Michael Kerrisk (man-pages) @ 2012-10-22 21:43 UTC (permalink / raw)
  To: Kees Cook; +Cc: linux-man, linux-doc, linux-kernel, wad

>> If the CONFIG_SECCOMP_FILTER permits fork(), is the seccomp setting
>> inherited across fork()? Similar question for execve().
>
> Yes for both. Additionally, the filters are cumulative. (If the
> filters allows prctl, additional filters can be appended; they are run
> in order until the first non-allow result is seen.)

Thanks. I'll add some words to the man page.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2012-10-22 21:43 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2012-09-20 23:37 [RESEND][PATCH] prctl: update seccomp sections for mode 2 (BPF) Kees Cook
2012-09-20 23:37 ` Kees Cook
2012-10-22  4:56 ` Michael Kerrisk (man-pages)
2012-10-22  7:34   ` Michael Kerrisk (man-pages)
2012-10-22 15:15     ` Kees Cook
2012-10-22 21:43       ` Michael Kerrisk (man-pages)

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