• Ian Abbott's avatar
    staging: comedi: fix memory leak / bad pointer freeing for chanlist · 238b5ad8
    Ian Abbott authored
    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: default avatarH 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: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
comedi_fops.c 58.1 KB