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    Subject[PATCH v2 1/6] SUNRPC: fix pipe->ops cleanup on pipe dentry unlink
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    Date
    This patch looks late due to GSS AUTH patches sent already. But it fixes a flaw
    in RPC PipeFS pipes handling.
    I've added this patch in the series, because this series related to pipes. But
    it should be a part of previous series named "SUNPRC: cleanup PipeFS for
    network-namespace-aware users".

    Pipe dentry can be created and destroyed many times during pipe life cycle.
    This actually means, that we can't set pipe->ops to NULL in rpc_close_pipes()
    and use this variable as a flag, indicating, that pipe's dentry is unlinking.
    To follow this restriction, this patch replaces "pipe->ops = NULL" assignment
    and checks for NULL with "pipe->dentry = NULL" assignment and checks for
    NULL respectively.
    This patch also removes check for non-NULL pipe->ops (or pipe->dentry) in
    rpc_close_pipes() because it always non-NULL now.

    Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>

    ---
    net/sunrpc/rpc_pipe.c | 51 +++++++++++++++++++------------------------------
    1 files changed, 20 insertions(+), 31 deletions(-)

    diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
    index 8d74575..6415241 100644
    --- a/net/sunrpc/rpc_pipe.c
    +++ b/net/sunrpc/rpc_pipe.c
    @@ -86,10 +86,6 @@ rpc_timeout_upcall_queue(struct work_struct *work)
    void (*destroy_msg)(struct rpc_pipe_msg *);

    spin_lock(&pipe->lock);
    - if (pipe->ops == NULL) {
    - spin_unlock(&pipe->lock);
    - return;
    - }
    destroy_msg = pipe->ops->destroy_msg;
    if (pipe->nreaders == 0) {
    list_splice_init(&pipe->pipe, &free_list);
    @@ -135,8 +131,6 @@ rpc_queue_upcall(struct rpc_pipe *pipe, struct rpc_pipe_msg *msg)
    int res = -EPIPE;

    spin_lock(&pipe->lock);
    - if (pipe->ops == NULL)
    - goto out;
    if (pipe->nreaders) {
    list_add_tail(&msg->list, &pipe->pipe);
    pipe->pipelen += msg->len;
    @@ -150,7 +144,6 @@ rpc_queue_upcall(struct rpc_pipe *pipe, struct rpc_pipe_msg *msg)
    pipe->pipelen += msg->len;
    res = 0;
    }
    -out:
    spin_unlock(&pipe->lock);
    wake_up(&pipe->waitq);
    return res;
    @@ -167,27 +160,23 @@ static void
    rpc_close_pipes(struct inode *inode)
    {
    struct rpc_pipe *pipe = RPC_I(inode)->pipe;
    - const struct rpc_pipe_ops *ops;
    int need_release;
    + LIST_HEAD(free_list);

    mutex_lock(&inode->i_mutex);
    - ops = pipe->ops;
    - if (ops != NULL) {
    - LIST_HEAD(free_list);
    - spin_lock(&pipe->lock);
    - need_release = pipe->nreaders != 0 || pipe->nwriters != 0;
    - pipe->nreaders = 0;
    - list_splice_init(&pipe->in_upcall, &free_list);
    - list_splice_init(&pipe->pipe, &free_list);
    - pipe->pipelen = 0;
    - pipe->ops = NULL;
    - spin_unlock(&pipe->lock);
    - rpc_purge_list(pipe, &free_list, ops->destroy_msg, -EPIPE);
    - pipe->nwriters = 0;
    - if (need_release && ops->release_pipe)
    - ops->release_pipe(inode);
    - cancel_delayed_work_sync(&pipe->queue_timeout);
    - }
    + spin_lock(&pipe->lock);
    + need_release = pipe->nreaders != 0 || pipe->nwriters != 0;
    + pipe->nreaders = 0;
    + list_splice_init(&pipe->in_upcall, &free_list);
    + list_splice_init(&pipe->pipe, &free_list);
    + pipe->pipelen = 0;
    + pipe->dentry = NULL;
    + spin_unlock(&pipe->lock);
    + rpc_purge_list(pipe, &free_list, pipe->ops->destroy_msg, -EPIPE);
    + pipe->nwriters = 0;
    + if (need_release && pipe->ops->release_pipe)
    + pipe->ops->release_pipe(inode);
    + cancel_delayed_work_sync(&pipe->queue_timeout);
    rpc_inode_setowner(inode, NULL);
    mutex_unlock(&inode->i_mutex);
    }
    @@ -224,7 +213,7 @@ rpc_pipe_open(struct inode *inode, struct file *filp)
    int res = -ENXIO;

    mutex_lock(&inode->i_mutex);
    - if (pipe->ops == NULL)
    + if (pipe->dentry == NULL)
    goto out;
    first_open = pipe->nreaders == 0 && pipe->nwriters == 0;
    if (first_open && pipe->ops->open_pipe) {
    @@ -250,7 +239,7 @@ rpc_pipe_release(struct inode *inode, struct file *filp)
    int last_close;

    mutex_lock(&inode->i_mutex);
    - if (pipe->ops == NULL)
    + if (pipe->dentry == NULL)
    goto out;
    msg = filp->private_data;
    if (msg != NULL) {
    @@ -291,7 +280,7 @@ rpc_pipe_read(struct file *filp, char __user *buf, size_t len, loff_t *offset)
    int res = 0;

    mutex_lock(&inode->i_mutex);
    - if (pipe->ops == NULL) {
    + if (pipe->dentry == NULL) {
    res = -EPIPE;
    goto out_unlock;
    }
    @@ -334,7 +323,7 @@ rpc_pipe_write(struct file *filp, const char __user *buf, size_t len, loff_t *of

    mutex_lock(&inode->i_mutex);
    res = -EPIPE;
    - if (pipe->ops != NULL)
    + if (pipe->dentry != NULL)
    res = pipe->ops->downcall(filp, buf, len);
    mutex_unlock(&inode->i_mutex);
    return res;
    @@ -349,7 +338,7 @@ rpc_pipe_poll(struct file *filp, struct poll_table_struct *wait)
    poll_wait(filp, &pipe->waitq, wait);

    mask = POLLOUT | POLLWRNORM;
    - if (pipe->ops == NULL)
    + if (pipe->dentry == NULL)
    mask |= POLLERR | POLLHUP;
    if (filp->private_data || !list_empty(&pipe->pipe))
    mask |= POLLIN | POLLRDNORM;
    @@ -366,7 +355,7 @@ rpc_pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
    switch (cmd) {
    case FIONREAD:
    spin_lock(&pipe->lock);
    - if (pipe->ops == NULL) {
    + if (pipe->dentry == NULL) {
    spin_unlock(&pipe->lock);
    return -EPIPE;
    }


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