Messages in this thread | | | Date | Sun, 28 Jul 2013 12:25:33 +0200 | From | Gabriel de Perthuis <> | Subject | Re: [PATCH] um: Accept /dev/fd/* uml block devices |
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Le dim. 28 juil. 2013 10:12:37 CEST, Richard Weinberger a écrit : > Am 27.07.2013 17:23, schrieb Gabriel de Perthuis: >> Useful for >> * limiting privileges >> * opening block devices O_EXCL > > So, the goal of this patch is to allow passing a file descriptor > number as block device instead of a file?
Yes. It turns out it already works, but not after dropping privileges.
> I assume you have already a wrapper around UML which exec()'s it such that > it can reuse a fd?
Yes, vido: https://github.com/g2p/vido
Here's the relevant commit: https://github.com/g2p/vido/commit/42d4b86eab13d90ee63138b73146485dc4e47ec6
>> Use dup to work around the fact /proc/self/fd >> can't be opened after dropping privileges. >> This proc behaviour doesn't match TLPI and might be a bug. >> >> Qemu has a slightly more complex fdset approach >> that provides fds with different access permissions. > > I really don't like that you patch os_open_file(), this is a > generic function.
The justification was that it unbreaks open("/dev/fd") to be more like standards suggest, but I can see how that makes it a special case.
> What about this one? > Allow ubda= (and all other UML block device kernel parameters) to > accept arguments like file:/foo/bar and fd:N. > Where N is a number and file: is default such that we do not break > old kernels.
Okay, I'll add a prefix. Maybe file:// + /abs/path | rel/path since that's already standard. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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