diff options
author | NeilBrown <neilb@suse.de> | 2014-08-04 16:24:00 +1000 |
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committer | Trond Myklebust <trond.myklebust@primarydata.com> | 2014-08-04 09:22:08 -0400 |
commit | 50d77739fa1972030daf1c8902404551e49bf232 (patch) | |
tree | 2e88b257ab14a66d790f5741137269965e06c444 /fs/nfs/dir.c | |
parent | f682a398b2e24ae0a775ddf37cced83b897198ee (diff) | |
download | linux-50d77739fa1972030daf1c8902404551e49bf232.tar.gz |
NFS: fix two problems in lookup_revalidate in RCU-walk
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> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Diffstat (limited to 'fs/nfs/dir.c')
-rw-r--r-- | fs/nfs/dir.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 1b5f38f48dab..36d921f0c602 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -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; } |