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

[Bernd Edlinger]

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@xxxxxxxxxx>
>     Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> 
> 
> I don't think I usually have this many typos.  Sigh.
> 

OK.

never mind,
Bernd.