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    Subject[PATCH 5.13 124/800] fuse: check connected before queueing on fpq->io
    Date
    From: Miklos Szeredi <mszeredi@redhat.com>

    commit 80ef08670d4c28a06a3de954bd350368780bcfef upstream.

    A request could end up on the fpq->io list after fuse_abort_conn() has
    reset fpq->connected and aborted requests on that list:

    Thread-1 Thread-2
    ======== ========
    ->fuse_simple_request() ->shutdown
    ->__fuse_request_send()
    ->queue_request() ->fuse_abort_conn()
    ->fuse_dev_do_read() ->acquire(fpq->lock)
    ->wait_for(fpq->lock) ->set err to all req's in fpq->io
    ->release(fpq->lock)
    ->acquire(fpq->lock)
    ->add req to fpq->io

    After the userspace copy is done the request will be ended, but
    req->out.h.error will remain uninitialized. Also the copy might block
    despite being already aborted.

    Fix both issues by not allowing the request to be queued on the fpq->io
    list after fuse_abort_conn() has processed this list.

    Reported-by: Pradeep P V K <pragalla@codeaurora.org>
    Fixes: fd22d62ed0c3 ("fuse: no fc->lock for iqueue parts")
    Cc: <stable@vger.kernel.org> # v4.2
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/fuse/dev.c | 9 +++++++++
    1 file changed, 9 insertions(+)

    --- a/fs/fuse/dev.c
    +++ b/fs/fuse/dev.c
    @@ -1272,6 +1272,15 @@ static ssize_t fuse_dev_do_read(struct f
    goto restart;
    }
    spin_lock(&fpq->lock);
    + /*
    + * Must not put request on fpq->io queue after having been shut down by
    + * fuse_abort_conn()
    + */
    + if (!fpq->connected) {
    + req->out.h.error = err = -ECONNABORTED;
    + goto out_end;
    +
    + }
    list_add(&req->list, &fpq->io);
    spin_unlock(&fpq->lock);
    cs->req = req;

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