kmod: Optional timeout on the wait in call_usermodehelper_exec

Andrew Hi

I'm picking on you because I don't have any one else to pick on. The 3 first patches here, are just good for today. Please see if you would like to take them? or tell me who should take them?

The 4th patch is an RFC, which got me looking into this.

My motivation is that I added yet another Kernel dependency on the call_usermodehelper() function and am not completely happy with the error case of having the user-mode program stuck forever. In such case I would like the Kernel part to timeout and properly error recover and clean up. So therefor the proposed 4th patch.

It is still in RFC because it is only lightly tested. I have booted with this patch and tested my use of it, with the new timeout. I have also dprinted the new reference counting introduced, and it does not look like we have any reference leaks.
Though I have not seen in dmesgs one of the three possible cases.

If the General Idea is acceptable and there is a chance this gets accepted, I will conduct heavy unit testing of all the cases and will resubmit the 4th patch.

So please review and tell me what you guys think.

[I have CCed all these that scripts/get_maintainers.pl suggested
so sorry for the noise for some]

The list of patches:
[PATCH 1/4] kmod: Unexport call_usermodehelper_freeinfo()
[PATCH 2/4] kmod: kmod: Convert two call sites to call_usermodehelper_fns() [PATCH 3/4] kmod: kmod: Move call_usermodehelper_fns() to .c file and unexport it's helpers

These 3 are good cleanups, regardless of any new fixtures

[RFC 4/4] {RFC} kmod.c: Add new call_usermodehelper_timeout() API

This patch is my motivation. Please review and comment on the new API, as well as the implementation details.

---
 fs/exec.c                   |    2 +-
 include/linux/kmod.h        |   47 +++++++++-----------------------
 kernel/kmod.c               |   62 +++++++++++++++++++++++++++++++++++-------
 kernel/sys.c                |   11 +------
 security/keys/request_key.c |   13 ++-------
 5 files changed, 71 insertions(+), 64 deletions(-)

---

Thanks
Boaz
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