| Message ID | 20220518225355.784371-13-ebiederm@xmission.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | ptrace: cleanups and calling do_cldstop with only siglock | expand |
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index d0527b6e2b29..fbadd2f21f09 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -689,7 +689,10 @@ static int ptrace_setoptions(struct task_struct *child, unsigned long data) if (ret) return ret; - /* Avoid intermediate state when all opts are cleared */ + /* + * With a frozen tracee, only the tracer modifies ->ptrace. + * Avoid intermediate state when all opts are cleared. + */ flags = child->ptrace; flags &= ~(PTRACE_O_MASK << PT_OPT_FLAG_SHIFT); flags |= (data << PT_OPT_FLAG_SHIFT);
The functions that change ->ptrace are: ptrace_attach, ptrace_traceme, ptrace_init_task, __ptrace_unlink, ptrace_setoptions. Except for ptrace_setoptions all of the places where ->ptrace is modified hold tasklist_lock for write, and either the tracee or the tracer is modifies ->ptrace. When ptrace_setoptions is called the tracee has been frozen with ptrace_freeze_traced, and most be explicitly unfrozen by the tracer before it can do anything. As ptrace_setoption is run in the tracer there can be no contention by the simple fact that the tracee can't run. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- kernel/ptrace.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)