audit: allow unsetting the loginuid (with priv)
If a task has CAP_AUDIT_CONTROL allow that task to unset their loginuid.
This would allow a child of that task to set their loginuid without
CAP_AUDIT_CONTROL. Thus when launching a new login daemon, a
priviledged helper would be able to unset the loginuid and then the
daemon, which may be malicious user facing, do not need priv to function
correctly.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1485e38..03c8d74 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1151,10 +1151,16 @@
goto out_free_page;
}
- kloginuid = make_kuid(file->f_cred->user_ns, loginuid);
- if (!uid_valid(kloginuid)) {
- length = -EINVAL;
- goto out_free_page;
+
+ /* is userspace tring to explicitly UNSET the loginuid? */
+ if (loginuid == AUDIT_UID_UNSET) {
+ kloginuid = INVALID_UID;
+ } else {
+ kloginuid = make_kuid(file->f_cred->user_ns, loginuid);
+ if (!uid_valid(kloginuid)) {
+ length = -EINVAL;
+ goto out_free_page;
+ }
}
length = audit_set_loginuid(kloginuid);