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Date: Mon, 01 Dec 2014 16:02:14 +1100 From: Michael Ellerman <mpe@...erman.id.au> To: Paul Mackerras <paulus@...ba.org> Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, Pekka Enberg <penberg@...nel.org>, linuxppc-dev@...abs.org, David Rientjes <rientjes@...gle.com>, Christoph Lameter <cl@...ux.com>, Joonsoo Kim <iamjoonsoo.kim@....com> Subject: Re: [PATCH v2] slab: Fix nodeid bounds check for non-contiguous node IDs On Mon, 2014-12-01 at 15:28 +1100, Paul Mackerras wrote: > The bounds check for nodeid in ____cache_alloc_node gives false > positives on machines where the node IDs are not contiguous, leading > to a panic at boot time. For example, on a POWER8 machine the node > IDs are typically 0, 1, 16 and 17. This means that num_online_nodes() > returns 4, so when ____cache_alloc_node is called with nodeid = 16 the > VM_BUG_ON triggers, like this: ... > > To fix this, we instead compare the nodeid with MAX_NUMNODES, and > additionally make sure it isn't negative (since nodeid is an int). > The check is there mainly to protect the array dereference in the > get_node() call in the next line, and the array being dereferenced is > of size MAX_NUMNODES. If the nodeid is in range but invalid (for > example if the node is off-line), the BUG_ON in the next line will > catch that. When did this break? How come we only just noticed? Also needs: Cc: stable@...r.kernel.org cheers -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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