aboutsummaryrefslogtreecommitdiff
path: root/security/commoncap.c
diff options
context:
space:
mode:
authorAndy Lutomirski <luto@amacapital.net>2012-04-12 16:47:50 -0500
committerJames Morris <james.l.morris@oracle.com>2012-04-14 11:13:18 +1000
commit259e5e6c75a910f3b5e656151dc602f53f9d7548 (patch)
tree4405fdf68238f2e33f27b04e8c37c9e29a2493d8 /security/commoncap.c
parent9ccf010f8172b699ea80178860e8ea228f7dce56 (diff)
downloadlinux-stericsson-259e5e6c75a910f3b5e656151dc602f53f9d7548.tar.gz
Add PR_{GET,SET}_NO_NEW_PRIVS to prevent execve from granting privs
With this change, calling prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) disables privilege granting operations at execve-time. For example, a process will not be able to execute a setuid binary to change their uid or gid if this bit is set. The same is true for file capabilities. Additionally, LSM_UNSAFE_NO_NEW_PRIVS is defined to ensure that LSMs respect the requested behavior. To determine if the NO_NEW_PRIVS bit is set, a task may call prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0); It returns 1 if set and 0 if it is not set. If any of the arguments are non-zero, it will return -1 and set errno to -EINVAL. (PR_SET_NO_NEW_PRIVS behaves similarly.) This functionality is desired for the proposed seccomp filter patch series. By using PR_SET_NO_NEW_PRIVS, it allows a task to modify the system call behavior for itself and its child tasks without being able to impact the behavior of a more privileged task. Another potential use is making certain privileged operations unprivileged. For example, chroot may be considered "safe" if it cannot affect privileged tasks. Note, this patch causes execve to fail when PR_SET_NO_NEW_PRIVS is set and AppArmor is in use. It is fixed in a subsequent patch. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Will Drewry <wad@chromium.org> Acked-by: Eric Paris <eparis@redhat.com> Acked-by: Kees Cook <keescook@chromium.org> v18: updated change desc v17: using new define values as per 3.4 Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'security/commoncap.c')
-rw-r--r--security/commoncap.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/security/commoncap.c b/security/commoncap.c
index 0cf4b53480a7..edd3918fac02 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -506,14 +506,17 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
skip:
/* Don't let someone trace a set[ug]id/setpcap binary with the revised
- * credentials unless they have the appropriate permit
+ * credentials unless they have the appropriate permit.
+ *
+ * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
*/
if ((new->euid != old->uid ||
new->egid != old->gid ||
!cap_issubset(new->cap_permitted, old->cap_permitted)) &&
bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
/* downgrade; they get no more than they had, and maybe less */
- if (!capable(CAP_SETUID)) {
+ if (!capable(CAP_SETUID) ||
+ (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
new->euid = new->uid;
new->egid = new->gid;
}