From da53be12bbb4fabbe2e9f6f908de0cf478b5161d Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 May 2013 15:22:44 -0700 Subject: 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 Signed-off-by: Al Viro --- fs/ncpfs/dir.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-) (limited to 'fs/ncpfs/dir.c') diff --git a/fs/ncpfs/dir.c b/fs/ncpfs/dir.c index 3bc105d36f10..3be047474bfc 100644 --- a/fs/ncpfs/dir.c +++ b/fs/ncpfs/dir.c @@ -73,10 +73,8 @@ const struct inode_operations ncp_dir_inode_operations = * 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 @@ static inline int ncp_case_sensitive(const struct inode *i) /* * 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 @@ ncp_hash_dentry(const struct dentry *dentry, const struct inode *inode, 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); -- cgit v1.2.3