| From 31a099dbd91e69fcab55eef4be15ed7a8c984918 Mon Sep 17 00:00:00 2001 |
| From: Guo Ren <guoren@linux.alibaba.com> |
| Date: Thu, 7 Apr 2022 15:33:20 +0800 |
| Subject: arm64: patch_text: Fixup last cpu should be master |
| |
| 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/patching.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- a/arch/arm64/kernel/patching.c |
| +++ b/arch/arm64/kernel/patching.c |
| @@ -117,8 +117,8 @@ 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]); |
