Re: [PATCH v2 4/5] exec: Move exec_mmap right after de_thread in flush_old_exec

Eric W. Biederman
2020-03-09T20:38:08Z

Bernd Edlinger <bernd.edlinger@hotmail.de> writes:

> On 3/9/20 8:58 PM, Eric W. Biederman wrote:
>>
>> Ok. I think this has it sorted:
>>
>> exec: Move exec_mmap right after de_thread in flush_old_exec
>>
>> I have read through the code in exec_mmap and I do not see anything
>> that depends on sighand or the sighand lock, or on signals in anyway
>> so this should be safe.
>>
>> This rearrangement of code has two significant benefits. It makes
>> the determination of passing the point of no return by testing bprm->mm
>> accurate. All failures prior to that point in flush_old_exec are
>> either truly recoverable or they are fatal.
>>
>> Further this consolidates all of the possible indefinite waits for
>> userspace together at the top of flush_old_exec. The possible wait
>> for a ptracer on PTRACE_EVENT_EXIT, the possible wait for a page fault
>> to be resolved in clear_child_tid, and the possible wait for a page
>> fault in exit_robust_list.
>>
>> This consolidation allows the creation of a mutex to replace
>> cred_guard_mutex that is not held over possible indefinite userspace
>> waits. Which will allow removing deadlock scenarios from the kernel.
>>
>> Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>>
>>
>> I don't think I usually have this many typos. Sigh.
>>
>
> OK.
>
> never mind,

No no. I really appreciate all of the scrutiny. Frequently the issues
that will produce typos or poor patch descriptions are also the issues
that will produce sloppy patches as well. I was just frustrated with
myself.

Eric