Re: [PATCH -mm 1/1] ptrace: PTRACE_GETFDPIC: fix the unsafe usage of child->mm

[David Howells]

Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

> Now that Mike Frysinger unified the FDPIC ptrace code, we can fix
> the unsafe usage of child->mm in ptrace_request(PTRACE_GETFDPIC).
> 
> We have the reference to task_struct, and ptrace_check_attach()
> verified the tracee is stopped. But nothing can protect from
> SIGKILL after that, we must not assume child->mm != NULL.
> 
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

Acked-by: David Howells <dhowells@xxxxxxxxxx>

Does it make sense to move the call to get_task_mm() up to sys_ptrace() since
several ptrace functions use it?  The mm pointer could then be handed down the
ptrace hierarchy.

David
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