From: Guo Ren guoren@linux.alibaba.com
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 guoren@linux.alibaba.com Signed-off-by: Guo Ren guoren@kernel.org Reviewed-by: Catalin Marinas catalin.marinas@arm.com Reviewed-by: Masami Hiramatsu mhiramat@kernel.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220407073323.743224-2-guoren@kernel.org Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/insn.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/arm64/kernel/insn.c +++ b/arch/arm64/kernel/insn.c @@ -207,8 +207,8 @@ static int __kprobes aarch64_insn_patch_ 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]);