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staging: comedi: fix memory leak for saved channel list

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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associated with the channel list is no longer valid.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.

Cc: stable@vger.kernel.org
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2012-09-19 19:37:39 +01:00 committed by Greg Kroah-Hartman
parent 6f73fbcec2
commit c8cad4c89e
1 changed files with 2 additions and 1 deletions
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3
drivers/staging/comedi/comedi_fops.c
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@ -1195,7 +1195,6 @@ static int do_cmd_ioctl(struct comedi_device *dev,
goto cleanup;
}
kfree(async->cmd.chanlist);
async->cmd = cmd;
async->cmd.data = NULL;
/* load channel/gain list */
@ -2033,6 +2032,8 @@ static void do_become_nonbusy(struct comedi_device *dev,
if (async) {
comedi_reset_async_buf(async);
async->inttrig = NULL;
kfree(async->cmd.chanlist);
async->cmd.chanlist = NULL;
} else {
dev_err(dev->class_dev,
"BUG: (?) do_become_nonbusy called with async=NULL\n");