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Diffstat (limited to 'Documentation/userspace-api/seccomp_filter.rst')
| -rw-r--r-- | Documentation/userspace-api/seccomp_filter.rst | 52 |
1 files changed, 50 insertions, 2 deletions
diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst index f71eb5ef1f2d..099c412951d6 100644 --- a/Documentation/userspace-api/seccomp_filter.rst +++ b/Documentation/userspace-api/seccomp_filter.rst @@ -87,11 +87,16 @@ Return values A seccomp filter may return any of the following values. If multiple filters exist, the return value for the evaluation of a given system call will always use the highest precedent value. (For example, -``SECCOMP_RET_KILL`` will always take precedence.) +``SECCOMP_RET_KILL_PROCESS`` will always take precedence.) In precedence order, they are: -``SECCOMP_RET_KILL``: +``SECCOMP_RET_KILL_PROCESS``: + Results in the entire process exiting immediately without executing + the system call. The exit status of the task (``status & 0x7f``) + will be ``SIGSYS``, not ``SIGKILL``. + +``SECCOMP_RET_KILL_THREAD``: Results in the task exiting immediately without executing the system call. The exit status of the task (``status & 0x7f``) will be ``SIGSYS``, not ``SIGKILL``. @@ -141,6 +146,15 @@ In precedence order, they are: allow use of ptrace, even of other sandboxed processes, without extreme care; ptracers can use this mechanism to escape.) +``SECCOMP_RET_LOG``: + Results in the system call being executed after it is logged. This + should be used by application developers to learn which syscalls their + application needs without having to iterate through multiple test and + development cycles to build the list. + + This action will only be logged if "log" is present in the + actions_logged sysctl string. + ``SECCOMP_RET_ALLOW``: Results in the system call being executed. @@ -169,7 +183,41 @@ The ``samples/seccomp/`` directory contains both an x86-specific example and a more generic example of a higher level macro interface for BPF program generation. +Sysctls +======= +Seccomp's sysctl files can be found in the ``/proc/sys/kernel/seccomp/`` +directory. Here's a description of each file in that directory: + +``actions_avail``: + A read-only ordered list of seccomp return values (refer to the + ``SECCOMP_RET_*`` macros above) in string form. The ordering, from + left-to-right, is the least permissive return value to the most + permissive return value. + + The list represents the set of seccomp return values supported + by the kernel. A userspace program may use this list to + determine if the actions found in the ``seccomp.h``, when the + program was built, differs from the set of actions actually + supported in the current running kernel. + +``actions_logged``: + A read-write ordered list of seccomp return values (refer to the + ``SECCOMP_RET_*`` macros above) that are allowed to be logged. Writes + to the file do not need to be in ordered form but reads from the file + will be ordered in the same way as the actions_avail sysctl. + + It is important to note that the value of ``actions_logged`` does not + prevent certain actions from being logged when the audit subsystem is + configured to audit a task. If the action is not found in + ``actions_logged`` list, the final decision on whether to audit the + action for that task is ultimately left up to the audit subsystem to + decide for all seccomp return values other than ``SECCOMP_RET_ALLOW``. + + The ``allow`` string is not accepted in the ``actions_logged`` sysctl + as it is not possible to log ``SECCOMP_RET_ALLOW`` actions. Attempting + to write ``allow`` to the sysctl will result in an EINVAL being + returned. Adding architecture support =========================== |