From: Daniel Henrique Barboza danielhb413@gmail.com
[ Upstream commit 749ed4a20657bcea66a6e082ca3dc0d228cbec80 ]
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 10f78fd0dabb ("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: 10f78fd0dabb ("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 --- arch/powerpc/mm/numa.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index 9d5f710d2c20..b9b7fefbb64b 100644 --- a/arch/powerpc/mm/numa.c +++ b/arch/powerpc/mm/numa.c @@ -956,7 +956,9 @@ static int __init parse_numa_properties(void) of_node_put(cpu); }
- node_set_online(nid); + /* node_set_online() is an UB if 'nid' is negative */ + if (likely(nid >= 0)) + node_set_online(nid); }
get_n_mem_cells(&n_mem_addr_cells, &n_mem_size_cells);