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    Subject[PATCH 6.0 166/862] rpmsg: char: Avoid double destroy of default endpoint
    Date
    From: Shengjiu Wang <shengjiu.wang@nxp.com>

    commit 467233a4ac29b215d492843d067a9f091e6bf0c5 upstream.

    The rpmsg_dev_remove() in rpmsg_core is the place for releasing
    this default endpoint.

    So need to avoid destroying the default endpoint in
    rpmsg_chrdev_eptdev_destroy(), this should be the same as
    rpmsg_eptdev_release(). Otherwise there will be double destroy
    issue that ept->refcount report warning:

    refcount_t: underflow; use-after-free.

    Call trace:
    refcount_warn_saturate+0xf8/0x150
    virtio_rpmsg_destroy_ept+0xd4/0xec
    rpmsg_dev_remove+0x60/0x70

    The issue can be reproduced by stopping remoteproc before
    closing the /dev/rpmsgX.

    Fixes: bea9b79c2d10 ("rpmsg: char: Add possibility to use default endpoint of the rpmsg device")
    Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
    Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
    Reviewed-by: Peng Fan <peng.fan@nxp.com>
    Cc: stable <stable@vger.kernel.org>
    Link: https://lore.kernel.org/r/1663725523-6514-1-git-send-email-shengjiu.wang@nxp.com
    Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/rpmsg/rpmsg_char.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/drivers/rpmsg/rpmsg_char.c
    +++ b/drivers/rpmsg/rpmsg_char.c
    @@ -76,7 +76,9 @@ int rpmsg_chrdev_eptdev_destroy(struct d

    mutex_lock(&eptdev->ept_lock);
    if (eptdev->ept) {
    - rpmsg_destroy_ept(eptdev->ept);
    + /* The default endpoint is released by the rpmsg core */
    + if (!eptdev->default_ept)
    + rpmsg_destroy_ept(eptdev->ept);
    eptdev->ept = NULL;
    }
    mutex_unlock(&eptdev->ept_lock);

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