On Tue, Aug 14, 2012 at 06:27:36PM -0300, Lucas De Marchi wrote: > On Tue, Aug 14, 2012 at 5:56 PM, Dmitry V. Levin wrote: > > > > The new edition of modprobe provided by kmod, unlike the old one from > > module-init-tools, doesn't honour blacklist by default when processing > > aliases. > > > > Back in 2005, when blacklist support in modprobe was first added for > > module-init-tools, it was implemented that way deliberately: > > http://lkml.org/lkml/2005/5/11/74 > > > > Since 2005 the feature became quite popular. In particular, it is used > > as a method to "unalias" all kinds of aliases for the given module. > > I'm aware of many default configurations where such constructs as > > "alias net-pf-3 off" were rewritten as "blacklist ax25". > > Unfortunately, these configurations not just break with migration from > > module-init-tools to kmod, but also introduce a vulnerability: an > > unprivileged user can use socket(2) syscall to make the kernel load > > various modules implementing rare network protocols which used to be > > blacklisted. Some of these modules had various security bugs in the past > > (like CVE-2009-2909 in ax25 mentioned above), and are likely to be less > > audited than more widespread network protocols, so unguarded access to > > these modules poses a security risk. > > > > What I'd like to know is what was the rationale for the change in modprobe > > What's the change? As I said, modprobe from module-init-tools honours blacklist by default when processing aliases, but modprobe from kmod doesn't. For example, "blacklist ax25" makes "modprobe net-pf-3" a noop in case of module-init-tools, while the modprobe from kmod loads ax25 despite of blacklist. Assuming that kmod aims to replace module-init-tools, this qualifies as a change in behaviour. > > behaviour and how do you propose to deal with the security regression it > > introduced? > > there shouldn't be a change in behaviour. Could you provide an example > the results are different and if possible add it to > testsuite/test-blacklist.c? Is testsuite/test-blacklist.c an appropriate place for modprobe tests? It rather looks as a place for libkmod tests. -- ldv
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