staging: comedi: fix memory leak / bad pointer freeing for chanlist
As a follow-up to commit 6cab7a37 ("staging: comedi: (regression) channel list must be set for COMEDI_CMD ioctl"), Hartley Sweeten pointed out another couple of bugs stemming from commit 6cab7a37 ("staging: comedi: comedi_fops: introduce __comedi_get_user_chanlist()"). Firstly, `do_cmdtest_ioctl()` never frees the kernel copy of the user chanlist allocated by `__comedi_get_user_chanlist()`, so that memory is leaked. Fix it by freeing the allocated kernel memory pointed to by `cmd.chanlist` before that pointer is overwritten with its original pointer to user memory before `cmd` is copied back to user-space. Secondly, if `__comedi_get_user_chanlist()` returns an error, `cmd->chanlist` is left unchanged and in fact will be a pointer to user memory. This causes `do_cmd_ioctl()` to `goto cleanup` and call `do_become_nonbusy()` which would attempt to free the memory pointed to by the user-space pointer. Fix it by setting `cmd->chanlist` to NULL at the start of `__comedi_get_user_chanlist()`. Fixes: c6cd0eef ("staging: comedi: comedi_fops: introduce __comedi_get_user_chanlist()") Reported-by:H Hartley Sweeten <hsweeten@visionengravers.com> Cc: <stable@vger.kernel.org> # 3.15.y 3.16.y 3.17.y: 6cab7a37 Cc: <stable@vger.kernel.org> # 3.15.y 3.16.y 3.17.y Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
parent
0ea6fa03
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