From 22ff3a2f65e4e233a0d5ed4b74f02d0fef602828 Mon Sep 17 00:00:00 2001 From: Guo Ren Date: Thu, 7 Apr 2022 15:33:20 +0800 Subject: [PATCH] arm64: patch_text: Fixup last cpu should be master commit 31a099dbd91e69fcab55eef4be15ed7a8c984918 upstream. These patch_text implementations are using stop_machine_cpuslocked infrastructure with atomic cpu_count. The original idea: When the master CPU patch_text, the others should wait for it. But current implementation is using the first CPU as master, which couldn't guarantee the remaining CPUs are waiting. This patch changes the last CPU as the master to solve the potential risk. Fixes: ae16480785de ("arm64: introduce interfaces to hotpatch kernel and module code") Signed-off-by: Guo Ren Signed-off-by: Guo Ren Reviewed-by: Catalin Marinas Reviewed-by: Masami Hiramatsu Cc: Link: https://lore.kernel.org/r/20220407073323.743224-2-guoren@kernel.org Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/insn.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c index 6998ff9c1427..6fdba70d7179 100644 --- a/arch/arm64/kernel/insn.c +++ b/arch/arm64/kernel/insn.c @@ -234,8 +234,8 @@ static int __kprobes aarch64_insn_patch_text_cb(void *arg) int i, ret = 0; struct aarch64_insn_patch *pp = arg; - /* The first CPU becomes master */ - if (atomic_inc_return(&pp->cpu_count) == 1) { + /* The last CPU becomes master */ + if (atomic_inc_return(&pp->cpu_count) == num_online_cpus()) { for (i = 0; ret == 0 && i < pp->insn_cnt; i++) ret = aarch64_insn_patch_text_nosync(pp->text_addrs[i], pp->new_insns[i]);