This is a note to let you know that I've just added the patch titled powerpc/mm/numa: skip NUMA_NO_NODE onlining in parse_numa_properties() to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-mm-numa-skip-numa_no_node-onlining-in-parse_.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 69513628ee40ee9a4316732c984b949977d84034 Author: Daniel Henrique Barboza <danielhb413@xxxxxxxxx> Date: Thu Feb 24 15:23:12 2022 -0300 powerpc/mm/numa: skip NUMA_NO_NODE onlining in parse_numa_properties() [ 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@xxxxxxxxxx> Signed-off-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220224182312.1012527-1-danielhb413@xxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c index 59d3cfcd7887..5fb829256b59 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);