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| author | Andy Lutomirski <luto@amacapital.net> | 2012-07-05 22:23:24 +0400 |
|---|---|---|
| committer | James Morris <james.l.morris@oracle.com> | 2012-07-07 18:25:48 +0400 |
| commit | c540521bba5d2f24bd2c0417157bfaf8b85e2eee (patch) | |
| tree | 64d387e5910f377b178bb168659684a0f09b20c2 | |
| parent | 26c439d4005d94b8da28e023e285fd4a9943470e (diff) | |
| download | linux-c540521bba5d2f24bd2c0417157bfaf8b85e2eee.tar.xz | |
security: Minor improvements to no_new_privs documentation
The documentation didn't actually mention how to enable no_new_privs.
This also adds a note about possible interactions between
no_new_privs and LSMs (i.e. why teaching systemd to set no_new_privs
is not necessarily a good idea), and it references the new docs
from include/linux/prctl.h.
Suggested-by: Rob Landley <rob@landley.net>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.l.morris@oracle.com>
| -rw-r--r-- | Documentation/prctl/no_new_privs.txt | 7 | ||||
| -rw-r--r-- | include/linux/prctl.h | 2 |
2 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/prctl/no_new_privs.txt b/Documentation/prctl/no_new_privs.txt index cb705ec69abe..f7be84fba910 100644 --- a/Documentation/prctl/no_new_privs.txt +++ b/Documentation/prctl/no_new_privs.txt @@ -25,6 +25,13 @@ bits will no longer change the uid or gid; file capabilities will not add to the permitted set, and LSMs will not relax constraints after execve. +To set no_new_privs, use prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0). + +Be careful, though: LSMs might also not tighten constraints on exec +in no_new_privs mode. (This means that setting up a general-purpose +service launcher to set no_new_privs before execing daemons may +interfere with LSM-based sandboxing.) + Note that no_new_privs does not prevent privilege changes that do not involve execve. An appropriately privileged task can still call setuid(2) and receive SCM_RIGHTS datagrams. diff --git a/include/linux/prctl.h b/include/linux/prctl.h index 3988012255dc..289760f424aa 100644 --- a/include/linux/prctl.h +++ b/include/linux/prctl.h @@ -141,6 +141,8 @@ * Changing LSM security domain is considered a new privilege. So, for example, * asking selinux for a specific new context (e.g. with runcon) will result * in execve returning -EPERM. + * + * See Documentation/prctl/no_new_privs.txt for more details. */ #define PR_SET_NO_NEW_PRIVS 38 #define PR_GET_NO_NEW_PRIVS 39 |