Re: [PATCH] capability: WARN when invalid capability is requested rather than BUG/panic
On Tue, 30 Sep 2008, Eric Paris wrote:
This patch adds a WARN_ONCE() to cap_capable() so we will stop
dereferencing random spots of memory and will cleanly tell the obviously
broken driver that it doesn't have that ridiculous permissions. No idea
if the driver is going to handle EPERM but anything that calls capable
and doesn't expect a denial has got to be the worst piece of code ever
written..... I could return EINVAL, but I think its clear that noone
has capabilities over 64 so clearly they don't have that permission.
This 'could' be considered a regression since 2.6.24. Neither SELinux
nor the capabilities system had a problem with ginormous request values
until we got 64 bit support, although this is OBVIOUSLY a bug with the
out of tree closed source driver....
An issue here is whether we should be adding workarounds in the mainline
kernel for buggy closed drivers. Papering over problems rather than
getting them fixed does not seem like a winning approach. Especially
problems which are unexpectedly messing with kernel security APIs.
Also, won't this encourage vendors of such drivers to continue with this
behavior, while discouraging those vendors who are doing the right thing?
Do we know if this even really helps the user? For all we know, the
driver may simply crash differently with an -EPERM.
- James
--
James Morris
<jmorris@xxxxxxxxx>
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