seccomp: Operation for checking if an action is available

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Userspace code that needs to check if the kernel supports a given action
may not be able to use the /proc/sys/kernel/seccomp/actions_avail
sysctl. The process may be running in a sandbox and, therefore,
sufficient filesystem access may not be available. This patch adds an
operation to the seccomp(2) syscall that allows userspace code to ask
the kernel if a given action is available.

If the action is supported by the kernel, 0 is returned. If the action
is not supported by the kernel, -1 is returned with errno set to
-EOPNOTSUPP. If this check is attempted on a kernel that doesn't support
this new operation, -1 is returned with errno set to -EINVAL meaning
that userspace code will have the ability to differentiate between the
two error cases.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Suggested-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Kees Cook <keescook@chromium.org>

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This commit is contained in:

Tyler Hicks 2017-08-11 04:33:53 +00:00 • committed by Kees Cook

parent 8e5f1ad116

commit d612b1fd80

3 changed files with 65 additions and 2 deletions

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5

include/uapi/linux/seccomp.h

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26

kernel/seccomp.c

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36

tools/testing/selftests/seccomp/seccomp_bpf.c

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