Don't pass inode to ->d_hash() and ->d_compare()
Instances either don't look at it at all (the majority of cases) or
only want it to find the superblock (which can be had as dentry->d_sb).
A few cases that want more are actually safe with dentry->d_inode -
the only precaution needed is the check that it hadn't been replaced with
NULL by rmdir() or by overwriting rename(), which case should be simply
treated as cache miss.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/ncpfs/dir.c b/fs/ncpfs/dir.c
index 3bc105d..3be0474 100644
--- a/fs/ncpfs/dir.c
+++ b/fs/ncpfs/dir.c
@@ -73,10 +73,8 @@
* Dentry operations routines
*/
static int ncp_lookup_validate(struct dentry *, unsigned int);
-static int ncp_hash_dentry(const struct dentry *, const struct inode *,
- struct qstr *);
-static int ncp_compare_dentry(const struct dentry *, const struct inode *,
- const struct dentry *, const struct inode *,
+static int ncp_hash_dentry(const struct dentry *, struct qstr *);
+static int ncp_compare_dentry(const struct dentry *, const struct dentry *,
unsigned int, const char *, const struct qstr *);
static int ncp_delete_dentry(const struct dentry *);
@@ -119,11 +117,19 @@
/*
* Note: leave the hash unchanged if the directory
* is case-sensitive.
+ *
+ * Accessing the parent inode can be racy under RCU pathwalking.
+ * Use ACCESS_ONCE() to make sure we use _one_ particular inode,
+ * the callers will handle races.
*/
static int
-ncp_hash_dentry(const struct dentry *dentry, const struct inode *inode,
- struct qstr *this)
+ncp_hash_dentry(const struct dentry *dentry, struct qstr *this)
{
+ struct inode *inode = ACCESS_ONCE(dentry->d_inode);
+
+ if (!inode)
+ return 0;
+
if (!ncp_case_sensitive(inode)) {
struct super_block *sb = dentry->d_sb;
struct nls_table *t;
@@ -140,14 +146,24 @@
return 0;
}
+/*
+ * Accessing the parent inode can be racy under RCU pathwalking.
+ * Use ACCESS_ONCE() to make sure we use _one_ particular inode,
+ * the callers will handle races.
+ */
static int
-ncp_compare_dentry(const struct dentry *parent, const struct inode *pinode,
- const struct dentry *dentry, const struct inode *inode,
+ncp_compare_dentry(const struct dentry *parent, const struct dentry *dentry,
unsigned int len, const char *str, const struct qstr *name)
{
+ struct inode *pinode;
+
if (len != name->len)
return 1;
+ pinode = ACCESS_ONCE(parent->d_inode);
+ if (!pinode)
+ return 1;
+
if (ncp_case_sensitive(pinode))
return strncmp(str, name->name, len);