selinux: stop passing MAY_NOT_BLOCK to the AVC upon follow_link

commit bda0be7ad9948 ("security: make inode_follow_link RCU-walk aware")
switched selinux_inode_follow_link() to use avc_has_perm_flags() and
pass down the MAY_NOT_BLOCK flag if called during RCU walk.  However,
the only test of MAY_NOT_BLOCK occurs during slow_avc_audit()
and only if passing an inode as audit data (LSM_AUDIT_DATA_INODE).  Since
selinux_inode_follow_link() passes a dentry directly, passing MAY_NOT_BLOCK
here serves no purpose.  Switch selinux_inode_follow_link() to use
avc_has_perm() and drop avc_has_perm_flags() since there are no other
users.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>

3 files changed, 4 insertions, 30 deletions

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 5de18a6d5c3f..9b63d8ee1687 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -867,9 +867,8 @@ static int avc_update_node(struct selinux_avc *avc,
          * permissive mode that only appear when in enforcing mode.
          *
          * See the corresponding handling in slow_avc_audit(), and the
-         * logic in selinux_inode_follow_link and selinux_inode_permission
-         * for the VFS MAY_NOT_BLOCK flag, which is transliterated into
-         * AVC_NONBLOCKING for avc_has_perm_noaudit().
+         * logic in selinux_inode_permission for the MAY_NOT_BLOCK flag,
+         * which is transliterated into AVC_NONBLOCKING.
          */
         if (flags & AVC_NONBLOCKING)
                 return 0;
@@ -1209,25 +1208,6 @@ int avc_has_perm(struct selinux_state *state, u32 ssid, u32 tsid, u16 tclass,
         return rc;
 }
 
-int avc_has_perm_flags(struct selinux_state *state,
-                       u32 ssid, u32 tsid, u16 tclass, u32 requested,
-                       struct common_audit_data *auditdata,
-                       int flags)
-{
-        struct av_decision avd;
-        int rc, rc2;
-
-        rc = avc_has_perm_noaudit(state, ssid, tsid, tclass, requested,
-                                  (flags & MAY_NOT_BLOCK) ? AVC_NONBLOCKING : 0,
-                                  &avd);
-
-        rc2 = avc_audit(state, ssid, tsid, tclass, requested, &avd, rc,
-                        auditdata, flags);
-        if (rc2)
-                return rc2;
-        return rc;
-}
-
 u32 avc_policy_seqno(struct selinux_state *state)
 {
         return state->avc->avc_cache.latest_notif;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 7f6068489a02..f08a0f201967 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2925,9 +2925,8 @@ static int selinux_inode_follow_link(struct dentry *dentry, struct inode *inode,
         if (IS_ERR(isec))
                 return PTR_ERR(isec);
 
-        return avc_has_perm_flags(&selinux_state,
-                                  sid, isec->sid, isec->sclass, FILE__READ, &ad,
-                                  rcu ? MAY_NOT_BLOCK : 0);
+        return avc_has_perm(&selinux_state,
+                            sid, isec->sid, isec->sclass, FILE__READ, &ad);
 }
 
 static noinline int audit_inode_permission(struct inode *inode,
diff --git a/security/selinux/include/avc.h b/security/selinux/include/avc.h
index 74ea50977c20..7be0e1e90e8b 100644
--- a/security/selinux/include/avc.h
+++ b/security/selinux/include/avc.h
@@ -153,11 +153,6 @@ int avc_has_perm(struct selinux_state *state,
                  u32 ssid, u32 tsid,
                  u16 tclass, u32 requested,
                  struct common_audit_data *auditdata);
-int avc_has_perm_flags(struct selinux_state *state,
-                       u32 ssid, u32 tsid,
-                       u16 tclass, u32 requested,
-                       struct common_audit_data *auditdata,
-                       int flags);
 
 int avc_has_extended_perms(struct selinux_state *state,
                            u32 ssid, u32 tsid, u16 tclass, u32 requested,