[RFC PATCH 2/2] selinux: fall back to ref-walk upon LSM_AUDIT_DATA_DENTRY too

[Stephen Smalley <sds@tycho.nsa.gov>]

commit bda0be7ad994 ("security: make inode_follow_link RCU-walk aware")
passed down the rcu flag to the SELinux AVC, but failed to adjust the
test in slow_avc_audit() to also return -ECHILD on LSM_AUDIT_DATA_DENTRY.
Previously, we only returned -ECHILD if generating an audit record with
LSM_AUDIT_DATA_INODE since this was only relevant from inode_permission.
Return -ECHILD on either LSM_AUDIT_DATA_INODE or LSM_AUDIT_DATA_DENTRY.
LSM_AUDIT_DATA_INODE only requires this handling due to the fact
that dump_common_audit_data() calls d_find_alias() and collects the
dname from the result if any.
Other cases that might require similar treatment in the future are
LSM_AUDIT_DATA_PATH and LSM_AUDIT_DATA_FILE if any hook that takes
a path or file is called under RCU-walk.

Fixes: bda0be7ad994 ("security: make inode_follow_link RCU-walk aware")
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
---
 security/selinux/avc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index 74c43ebe34bb..f1fa1072230c 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -779,7 +779,8 @@ noinline int slow_avc_audit(struct selinux_state *state,
 	 * during retry. However this is logically just as if the operation
 	 * happened a little later.
 	 */
-	if ((a->type == LSM_AUDIT_DATA_INODE) &&
+	if ((a->type == LSM_AUDIT_DATA_INODE ||
+	     a->type == LSM_AUDIT_DATA_DENTRY) &&
 	    (flags & MAY_NOT_BLOCK))
 		return -ECHILD;
 
-- 
2.23.0