From 451472dc178faf1dd3dff96e1ce67f9bdbf6f611 Mon Sep 17 00:00:00 2001
From: Daniel Henrique Barboza <danielhb413@gmail.com>
Date: Thu, 24 Feb 2022 15:23:12 -0300
Subject: [PATCH] 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@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 59d3cfcd78879..5fb829256b59d 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);
--
2.30.2