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    Subject[ 039/147] staging: comedi: fix memory leak for saved channel list
    3.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Ian Abbott <abbotti@mev.co.uk>

    commit c8cad4c89ee3b15935c532210ae6ebb5c0a2734d upstream.

    When `do_cmd_ioctl()` allocates memory for the kernel copy of a channel
    list, it frees any previously allocated channel list in
    `async->cmd.chanlist` and replaces it with the new one. However, if the
    device is ever removed (or "detached") the cleanup code in
    `cleanup_device()` in "drivers.c" does not free this memory so it is
    lost.

    A sensible place to free the kernel copy of the channel list is in
    `do_become_nonbusy()` as at that point the comedi asynchronous command
    associated with the channel list is no longer valid. Free the channel
    list in `do_become_nonbusy()` instead of `do_cmd_ioctl()` and clear the
    pointer to prevent it being freed more than once.

    Note that `cleanup_device()` could be called at an inappropriate time
    while the comedi device is open, but that's a separate bug not related
    to this this patch.

    Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    [bwh: Backported to 3.2: adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/staging/comedi/comedi_fops.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/drivers/staging/comedi/comedi_fops.c
    +++ b/drivers/staging/comedi/comedi_fops.c
    @@ -1088,7 +1088,6 @@ static int do_cmd_ioctl(struct comedi_de
    goto cleanup;
    }

    - kfree(async->cmd.chanlist);
    async->cmd = user_cmd;
    async->cmd.data = NULL;
    /* load channel/gain list */
    @@ -1833,6 +1832,8 @@ void do_become_nonbusy(struct comedi_dev
    if (async) {
    comedi_reset_async_buf(async);
    async->inttrig = NULL;
    + kfree(async->cmd.chanlist);
    + async->cmd.chanlist = NULL;
    } else {
    printk(KERN_ERR
    "BUG: (?) do_become_nonbusy called with async=0\n");



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