[PATCH 4.16 009/272] fix breakage caused by d_find_alias() semantics change

Greg Kroah-Hartman
2018-05-28T11:25:56Z

From: Al Viro <viro@zeniv.linux.org.uk>

commit b127125d9db23e4856156a7c909a3c8e18b69f99 upstream.

"VFS: don't keep disconnected dentries on d_anon" had a non-trivial
side-effect - d_unhashed() now returns true for those dentries,
making d_find_alias() skip them altogether. For most of its callers
that's fine - we really want a connected alias there. However,
there is a codepath where we relied upon picking such aliases
if nothing else could be found - selinux delayed initialization
of contexts for inodes on already mounted filesystems used to
rely upon that.

Cc: stable@kernel.org # f1ee616214cb "VFS: don't keep disconnected dentries on d_anon"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
security/selinux/hooks.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)

--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1532,8 +1532,15 @@ static int inode_doinit_with_dentry(stru
/* Called from d_instantiate or d_splice_alias. */
dentry = dget(opt_dentry);
} else {
- /* Called from selinux_complete_init, try to find a dentry. */
+ /*
+ * Called from selinux_complete_init, try to find a dentry.
+ * Some filesystems really want a connected one, so try
+ * that first. We could split SECURITY_FS_USE_XATTR in
+ * two, depending upon that...
+ */
dentry = d_find_alias(inode);
+ if (!dentry)
+ dentry = d_find_any_alias(inode);
}
if (!dentry) {
/*
@@ -1636,14 +1643,19 @@ static int inode_doinit_with_dentry(stru
if ((sbsec->flags & SE_SBGENFS) && !S_ISLNK(inode->i_mode)) {
/* We must have a dentry to determine the label on
* procfs inodes */
- if (opt_dentry)
+ if (opt_dentry) {
/* Called from d_instantiate or
* d_splice_alias. */
dentry = dget(opt_dentry);
- else
+ } else {
/* Called from selinux_complete_init, try to
- * find a dentry. */
+ * find a dentry. Some filesystems really want
+ * a connected one, so try that first.
+ */
dentry = d_find_alias(inode);
+ if (!dentry)
+ dentry = d_find_any_alias(inode);
+ }
/*
* This can be hit on boot when a file is accessed
* before the policy is loaded. When we load policy we