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[180.177.112.186]) by smtp.gmail.com with ESMTPSA id n72sm4529750pfd.202.2020.11.06.22.47.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2020 22:47:25 -0800 (PST) From: Eddy Wu X-Google-Original-From: Eddy Wu Date: Sat, 7 Nov 2020 14:47:22 +0800 To: oleg@redhat.com Cc: security@kernel.org, linux-kernel@vger.kernel.org, eddy_wu@trendmicro.com Subject: [PATCH] fork: fix copy_process(CLONE_PARENT) race with the exiting ->real_parent Message-ID: <20201107064722.GA139215@arch-e3.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org current->group_leader->exit_signal may change during copy_process() if current->real_parent exits, move the assignment inside tasklist_lock to avoid the race. Signed-off-by: Eddy Wu --- kernel/fork.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index da8d360fb032..7abda2a888a9 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2142,14 +2142,9 @@ static __latent_entropy struct task_struct *copy_process( /* ok, now we should be set up.. */ p->pid = pid_nr(pid); if (clone_flags & CLONE_THREAD) { - p->exit_signal = -1; p->group_leader = current->group_leader; p->tgid = current->tgid; } else { - if (clone_flags & CLONE_PARENT) - p->exit_signal = current->group_leader->exit_signal; - else - p->exit_signal = args->exit_signal; p->group_leader = p; p->tgid = p->pid; } @@ -2193,9 +2188,14 @@ static __latent_entropy struct task_struct *copy_process( if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { p->real_parent = current->real_parent; p->parent_exec_id = current->parent_exec_id; + if (clone_flags & CLONE_THREAD) + p->exit_signal = -1; + else + p->exit_signal = current->group_leader->exit_signal; } else { p->real_parent = current; p->parent_exec_id = current->self_exec_id; + p->exit_signal = args->exit_signal; } klp_copy_process(p); -- 2.17.1