Hello Kees, On Fri, Sep 21, 2012 at 1:37 AM, Kees Cook <keescook@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> > --- > 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@xxxxxxxxxxxx > -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/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
