[RFC][PATCH] fix breakage caused by d_find_alias() semantics change

* [RFC][PATCH] fix breakage caused by d_find_alias() semantics change
@ 2018-05-13 15:51 Al Viro
  2018-05-13 18:35 ` Linus Torvalds
  0 siblings, 1 reply; 8+ messages in thread
From: Al Viro @ 2018-05-13 15:51 UTC (permalink / raw)
  To: linux-fsdevel; +Cc: NeilBrown, Linus Torvalds

[will go into #fixes, unless somebody yells]

"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>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 4cafe6a19167..d3dd37578994 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1570,6 +1570,8 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 		} else {
 			/* Called from selinux_complete_init, try to find a dentry. */
 			dentry = d_find_alias(inode);
+			if (!dentry)
+				dentry = d_find_any_alias(inode);
 		}
 		if (!dentry) {
 			/*
@@ -1674,14 +1676,17 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
 		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. */
 				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

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