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| author | Miklos Szeredi <miklos@szeredi.hu> | 2013-09-05 14:39:11 +0200 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2013-09-05 22:23:50 +0200 |
| commit | eed810076685c77dc9a8c5c3593e641c93caed1c (patch) | |
| tree | 5aba507073b0a7e29dfa0739272dfeda16eb5e29 /fs/namespace.c | |
| parent | vfs: check submounts and drop atomically (diff) | |
| download | linux-eed810076685c77dc9a8c5c3593e641c93caed1c.tar.xz linux-eed810076685c77dc9a8c5c3593e641c93caed1c.zip | |
vfs: check unlinked ancestors before mount
We check submounts before doing d_drop() on a non-empty directory dentry in
NFS (have_submounts()), but we do not exclude a racing mount. Nor do we
prevent mounts to be added to the disconnected subtree using relative paths
after the d_drop().
This patch fixes these issues by checking for unlinked (unhashed, non-root)
ancestors before proceeding with the mount. This is done with rename
seqlock taken for write and with ->d_lock grabbed on each ancestor in turn,
including our dentry itself. This ensures that the only one of
check_submounts_and_drop() or has_unlinked_ancestor() can succeed.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 11 |
1 files changed, 5 insertions, 6 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index ad8ea9bc2518..5997887cc64a 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -611,6 +611,7 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry) { struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry); struct mountpoint *mp; + int ret; list_for_each_entry(mp, chain, m_hash) { if (mp->m_dentry == dentry) { @@ -626,14 +627,12 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry) if (!mp) return ERR_PTR(-ENOMEM); - spin_lock(&dentry->d_lock); - if (d_unlinked(dentry)) { - spin_unlock(&dentry->d_lock); + ret = d_set_mounted(dentry); + if (ret) { kfree(mp); - return ERR_PTR(-ENOENT); + return ERR_PTR(ret); } - dentry->d_flags |= DCACHE_MOUNTED; - spin_unlock(&dentry->d_lock); + mp->m_dentry = dentry; mp->m_count = 1; list_add(&mp->m_hash, chain); |