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    SubjectRe: [PATCH] fs: fcntl_setlease defies lease_init assumptions
    On 5/8/06, Linus Torvalds <torvalds@osdl.org> wrote:
    > > Ok, I was actually really surprised that we'd ever allow a non-slab page
    > > to be free'd as a slab or kmalloc allocation, without screaming very
    > > loudly indeed. That implies a lack of some pretty fundamental sanity
    > > checking by default in the slab layer (I suspect slab debugging turns it
    > > on, but even without it, that's just nasty).
    > >
    > > Can you see if this trivial patch at least causes a honking huge
    > > "kernel BUG" message to be triggered quickly?

    On 5/8/06, Pekka Enberg <penberg@cs.helsinki.fi> wrote:
    > page_get_cache and page_get_slab are too late. You would need to do
    > the check in __cache_free; otherwise the stack pointer goes to per-CPU
    > caches and can be given back by kmalloc(). Adding PageSlab debugging
    > to __cache_free is probably too much of a performance hit, though.

    Btw, CONFIG_DEBUG_SLAB should catch this case, see kfree_debugcheck()
    for details.

    Pekka
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