Re: [PATCH] usermodehelper: Fix -ENOMEM return logic

[David Howells <dhowells@redhat.com>]

Lucas De Marchi <lucas.demarchi@profusion.mobi> wrote:

> Callers of call_usermodehelper_fns() should check the return value and
> free themselves the data passed if the return is -ENOMEM. This is
> because the subprocess_info is allocated in this function, and if the
> allocation fail, the cleanup function cannot be called.
> 
> However call_usermodehelper_exec() may also return -ENOMEM, in which
> case the cleanup function is called. This means that if the caller
> checked the return code, it was risking running the cleanup twice (like
> kernel/sys.c:orderly_poweroff()) and if not, a leak could happen.
> 
> This patch fixes both call_usermodehelper_fns() to never call the
> cleanup function in case retval == -ENOMEM and also the callers to
> actually check the return value of this function.

I suspect it's probably better to always call the cleanup function from
call_usermodehelper_fns() rather than have the cleanup done by the caller in
some circumstances and not others - would it make sense to change the cleanup
function to take the pointer to the caller data rather than to take the
subprocess_info struct?

David