Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 2 Mar 2012 17:11:41 -0800 | Subject | Re: Word-at-a-time dcache name accesses (was Re: .. anybody know of any filesystems that depend on the exact VFS 'namehash' implementation?) |
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On Fri, Mar 2, 2012 at 5:02 PM, H. Peter Anvin <hpa@zytor.com> wrote: > > Note that does mean we need a guard page after each and every > discontiguous RAM range, not just the last one. Raising that issue > since we have had serious bugs in that area in the past.
Are you sure? I didn't think we even *mapped* things at that granularity.
We only really need a guard page at the end of an actual end-of-ram where we no longer have page tables and/or could hit device space.
Which in practice never actually is an issue on PC's - we already guard against BIOS usage just under the 0xA0000 address, and in practice there are always ACPI tables at the end of RAM (and on x86-32 we can't use highmem for filenames anyway, so that takes away *those* cases).
Which is why I think that for testing purposes we don't even need to care - it's basically a "can't happen" (not to mention that nobody actually uses PATH_MAX pathames).
For robustness and actual deployment, I do think that yes, we do want to make it an explicit rule.
Linus -- 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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