On Wednesday, September 24, 2008 4:15 pm Jiri Kosina wrote: > On Tue, 23 Sep 2008, David Miller wrote: > > I did some snooping around, and while doing so I noticed that the PCI > > mmap code for x86 doesn't do one bit of range checking on the size, or > > any other aspect of the request, wrt. the MMIO regions actually mapped > > in the BARs of the PCI device. > > Ugh, indeed. Added Ingo and Jesse to CC. > > > Yikes! > > > > It just does a reserve_memtype() on the address range, and says "ok". > > > > So if, for example, the X server tries to mmap() more than an MMIO bar > > actually maps, the kernel lets the user do this. > > > > It would be very interesting to add the appropriate checks to > > pci_mmap_page_range() in arch/x86/pci/i386.c, anyone who wants to do > > this can use the code in arch/sparc64/kernel/pci.c: > > __pci_mmap_make_offset() as a guide, and see what happens. > > Absolutely. Or we can even do some dirty hackery in userspace, like > LD_PRELOADing X server and checking mmaps() that are close to MMIO regions > of affected devices. > > > If the MMIO space regions of the video cards sit right before the > > E1000E ones on the effected systems, that would pretty much > > convince me that this is the kind of problem we are having here. > > Unfortunately, looking at the lspci outputs that are in > https://bugzilla.novell.com/show_bug.cgi?id=425480 it seems to me that the > MMIO regions are quite far away from each other. Moreover, we don't actually do any writing (that I know of) of the ROM image from the X drivers or the kernel. In fact, in many cases X should be accessing the RAM copy of the ROM at 0xc0000 rather than via the ROM BAR. That said, adding a check to the x86 code would be a good thing to do; I'll hack up a patch tomorrow unless someone beats me to it. -- Jesse Barnes, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
