ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes: > Bernd Edlinger <bernd.edlinger@xxxxxxxxxx> writes: > >> On 3/9/20 6:40 PM, Eric W. Biederman wrote: >>> Bernd Edlinger <bernd.edlinger@xxxxxxxxxx> writes: >>> >>>> On 3/8/20 10:38 PM, Eric W. Biederman wrote: >>>>> >>>>> The cred_guard_mutex is problematic. The cred_guard_mutex is held >>>>> over the userspace accesses as the arguments from userspace are read. >>>>> The cred_guard_mutex is held of PTRACE_EVENT_EXIT as the the other >>> ^ over >>>> >>>> ... is held while waiting for the trace parent to handle PTRACE_EVENT_EXIT >>>> or something? >>> >>> Yes. Let me see if I can phrase that better. >>> >>>> I wonder if we also should mention that >>>> it is held while waiting for the trace parent to >>>> receive the exit code with "wait"? >>> >>> I don't think we have to spell out the details of how it all works, >>> unless that makes things clearer. Kernel developers can be expected >>> to figure out how the kernel works. The critical thing is that it is >>> an indefinite wait for userspace to take action. >>> >>> But I will look. >>> >>>>> threads are killed. The cred_guard_mutex is held over >>>>> "put_user(0, tsk->clear_child_tid)" in exit_mm(). >>>>> >>>>> Any of those can result in deadlock, as the cred_guard_mutex is held >>>>> over a possible indefinite userspace waits for userspace. >>>>> >>>>> Add exec_update_mutex that is only held over exec updating process >>>> >>>> Add ? >>> >>> Yes. That is what the change does: add exec_update_mutex. >>> >> >> I just kind of missed the "subject" in this sentence, >> like "This patch adds an exec_update_mutex that is ..." >> but english is a foreign language for me, so may be okay as is. > > English has a lot of options. I think this is a stylistic difference. > > Instead of being an observer and describing what the change does: > "This patch adds exec_update_mutex ..." > > I was being there in the moment and saying/commading what is happening: > "Add exec_update_mutex ..." > > Using the more immdediate form ends up with more concise and clearer > sentences. > > Every one of my writing teachers in school emphasized that point > and I see the who it works when I write things. But writing is hard and > I still tend toward long rambling sentences with many qualifiers that > confuse and detract from the point rather than make it clear what is > happening. And reading through it all now I can see your confusion. That description of my changes was not well done. Reworking it now. Eric
