Messages in this thread | | | Date | Mon, 29 Jun 2009 21:54:10 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v2] RO/NX protection for loadable kernel modules |
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* Arjan van de Ven <arjan@infradead.org> wrote:
> On Mon, 29 Jun 2009 11:16:40 -0400 > Siarhei Liakh <sliakh.lkml@gmail.com> wrote: > > > This patch is a logical extension of the protection provided by > > CONFIG_DEBUG_RODATA to LKMs. The protection is provided by splitting > > module_core and module_init into three logical parts each and setting > > appropriate page access permissions for each individual section: > > > > 1. Code: RO+X > > 2. RO data: RO+NX > > 3. RW data: RW+NX > > > > In order to achieve proper protection, layout_sections() have been > > modified to align each of the three parts mentioned above onto page > > boundary. Next, the corresponding page access permissions are set > > right before successful exit from load_module(). Further, > > module_free() have been modified to set module_core or module_init as > > RW+NX right before calling vfree(). Functionality of this patch is > > enabled only when CONFIG_DEBUG_RODATA defined at compile time. > > > > This is the second revision of the patch: it have been re-written to > > reduce the number of #ifdefs and to make it architecture-agnostic. > > Code formatting have been corrected also. > > > > you can still go one step further.... > there is no downside to doing NX at all for modules, except for the 3 > sections now each being page aligned thing. So in principle NX should > just not be part of any ifdef, only the alignment has any justification > for being so. > What you can do in the !CONFIG_OPTION case, is treating the "overlap" > pages as "most permissive goes"..... if you do that you should have 1 > ifdef in total. > > (and one can still argue that making this an option is not even > worth that, and just always do it unconditional)
agreed.
Ingo
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