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ceph: clean up unsafe d_parent accesses in build_dentry_path
While we hold a reference to the dentry when build_dentry_path is called, we could end up racing with a rename that changes d_parent. Handle that situation correctly, by using the rcu_read_lock to ensure that the parent dentry and inode stick around long enough to safely check ceph_snap and ceph_ino. Link: http://tracker.ceph.com/issues/18148 Signed-off-by: Jeff Layton <jlayton@redhat.com> Reviewed-by: Yan, Zheng <zyan@redhat.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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1 changed files with 7 additions and 2 deletions
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@ -1800,13 +1800,18 @@ static int build_dentry_path(struct dentry *dentry,
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int *pfreepath)
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{
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char *path;
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struct inode *dir;
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if (ceph_snap(d_inode(dentry->d_parent)) == CEPH_NOSNAP) {
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*pino = ceph_ino(d_inode(dentry->d_parent));
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rcu_read_lock();
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dir = d_inode_rcu(dentry->d_parent);
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if (dir && ceph_snap(dir) == CEPH_NOSNAP) {
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*pino = ceph_ino(dir);
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rcu_read_unlock();
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*ppath = dentry->d_name.name;
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*ppathlen = dentry->d_name.len;
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return 0;
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}
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rcu_read_unlock();
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path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
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if (IS_ERR(path))
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return PTR_ERR(path);
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