@@ -1102,7 +1102,7 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
int error;
if (flags & LOOKUP_RCU) {
- parent = rcu_dereference(dentry->d_parent);
+ parent = ACCESS_ONCE(dentry->d_parent);
dir = ACCESS_ONCE(parent->d_inode);
if (!dir)
return -ECHILD;
@@ -1184,7 +1184,7 @@ out_set_verifier:
nfs_advise_use_readdirplus(dir);
out_valid_noent:
if (flags & LOOKUP_RCU) {
- if (parent != rcu_dereference(dentry->d_parent))
+ if (parent != ACCESS_ONCE(dentry->d_parent))
return -ECHILD;
} else
dput(parent);
@@ -1585,7 +1585,7 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
struct inode *dir;
if (flags & LOOKUP_RCU) {
- parent = rcu_dereference(dentry);
+ parent = ACCESS_ONCE(dentry->d_parent);
dir = ACCESS_ONCE(parent->d_inode);
if (!dir)
return -ECHILD;
@@ -1599,7 +1599,7 @@ static int nfs4_lookup_revalidate(struct dentry *dentry, unsigned int flags)
ret = -ECHILD;
if (!(flags & LOOKUP_RCU))
dput(parent);
- else if (parent != rcu_dereference(dentry))
+ else if (parent != ACCESS_ONCE(dentry->d_parent))
return -ECHILD;
goto out;
}
1/ rcu_dereference isn't correct: that field isn't RCU protected. It could potentially change at any time so ACCESS_ONCE might be justified. changes to ->d_parent are protected by ->d_seq. However that isn't always checked after ->d_revalidate is called, so it is safest to keep the double-check that ->d_parent hasn't changed at the end of these functions. 2/ in nfs4_lookup_revalidate, "->d_parent" was forgotten. So 'parent' was not the parent of 'dentry'. This fails safe is the context is that dentry->d_inode is NULL, and the result of parent->d_inode being NULL is that ECHILD is returned, which is always safe. Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: NeilBrown <neilb@suse.de> --- fs/nfs/dir.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html