Messages in this thread | | | Subject | Re: [PATCH] mm: fix invalid node in alloc_migrate_target() | From | Vlastimil Babka <> | Date | Thu, 31 Mar 2016 15:13:41 +0200 |
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On 03/29/2016 03:06 PM, Vlastimil Babka wrote: > On 03/25/2016 08:22 PM, Andrew Morton wrote: >> Also, mm/mempolicy.c:offset_il_node() worries me: >> >> do { >> nid = next_node(nid, pol->v.nodes); >> c++; >> } while (c <= target); >> >> Can't `nid' hit MAX_NUMNODES? > > AFAICS it can. interleave_nid() uses this and the nid is then used e.g. > in node_zonelist() where it's used for NODE_DATA(nid). That's quite > scary. It also predates git. Why don't we see crashes or KASAN finding this?
Ah, I see. In offset_il_node(), nid is initialized to -1, and the number of do-while iterations calling next_node() is up to the number of bits set in the pol->v.nodes bitmap, so it can't reach past the last set bit and return MAX_NUMNODES.
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