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    Subject[PATCH 5.3 054/193] ceph: dont try to handle hashed dentries in non-O_CREAT atomic_open
    Date
    From: Jeff Layton <jlayton@kernel.org>

    commit 5bb5e6ee6f5c557dcd19822eccd7bcced1e1a410 upstream.

    If ceph_atomic_open is handed a !d_in_lookup dentry, then that means
    that it already passed d_revalidate so we *know* that it's negative (or
    at least was very recently). Just return -ENOENT in that case.

    This also addresses a subtle bug in dentry handling. Non-O_CREAT opens
    call atomic_open with the parent's i_rwsem shared, but calling
    d_splice_alias on a hashed dentry requires the exclusive lock.

    If ceph_atomic_open receives a hashed, negative dentry on a non-O_CREAT
    open, and another client were to race in and create the file before we
    issue our OPEN, ceph_fill_trace could end up calling d_splice_alias on
    the dentry with the new inode with insufficient locks.

    Cc: stable@vger.kernel.org
    Reported-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Jeff Layton <jlayton@kernel.org>
    Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ceph/file.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/fs/ceph/file.c
    +++ b/fs/ceph/file.c
    @@ -458,6 +458,9 @@ int ceph_atomic_open(struct inode *dir,
    err = ceph_security_init_secctx(dentry, mode, &as_ctx);
    if (err < 0)
    goto out_ctx;
    + } else if (!d_in_lookup(dentry)) {
    + /* If it's not being looked up, it's negative */
    + return -ENOENT;
    }

    /* do the open */

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