Daniel Henrique Barboza 05abd49972 powerpc/mm/numa: skip NUMA_NO_NODE onlining in parse_numa_properties()
[ Upstream commit 749ed4a206 ]

Executing node_set_online() when nid = NUMA_NO_NODE results in an
undefined behavior. node_set_online() will call node_set_state(), into
__node_set(), into set_bit(), and since NUMA_NO_NODE is -1 we'll end up
doing a negative shift operation inside
arch/powerpc/include/asm/bitops.h. This potential UB was detected
running a kernel with CONFIG_UBSAN.

The behavior was introduced by commit 10f78fd0da ("powerpc/numa: Fix a
regression on memoryless node 0"), where the check for nid > 0 was
removed to fix a problem that was happening with nid = 0, but the result
is that now we're trying to online NUMA_NO_NODE nids as well.

Checking for nid >= 0 will allow node 0 to be onlined while avoiding
this UB with NUMA_NO_NODE.

Fixes: 10f78fd0da ("powerpc/numa: Fix a regression on memoryless node 0")
Reported-by: Ping Fang <pifang@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220224182312.1012527-1-danielhb413@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-04-08 14:40:19 +02:00
2022-04-08 14:40:18 +02:00
2022-03-28 09:57:11 +02:00

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