On 04/20, Cyrill Gorcunov wrote:
On Thu, Apr 19, 2012 at 09:20:05PM +0200, Oleg Nesterov wrote:On 04/19, Andrew Morton wrote:
From: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
Subject: c/r: prctl: update prctl_set_mm_exe_file() after mm->num_exe_file_vmas removal
[ fix for "c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-v2" from mm tree ]
After removing mm->num_exe_file_vmas kernel keeps mm->exe_file until final
mmput(), it never becomes NULL while task is alive.
We can check for other mapped files in mm instead of checking
mm->num_exe_file_vmas, and mark mm with flag MMF_EXE_FILE_CHANGED in order
to forbid second changing of mm->exe_file.
I lost the track a long ago.
Just one question, what does this "forbid second changing" actually mean?
Heh :) Oleg, it was actually your idea to make this feature "one-shot".
Heh, no ;)
IIRC, I only asked you what do you actually want,
Just one note for the record, prctl_set_mm_exe_file() does
if (mm->num_exe_file_vmas)
return -EBUSY;
We could do
if (mm->exe_file)
return -EBUSY;
This way "because this feature is a special to C/R" becomes
really true. IOW, you can't do PR_SET_MM_EXE_FILE twice.
I am fine either way, just I want to ensure you really want
the current version.
and only because it was documented as "feature is a special to C/R".
Once exe-file changed to a new value, it can't be changed again. The
reason was to bring at least minimum disturbance in sysadmins life.
You misunderstood. I am not arguing with "one-shot", I do not really
care.
My question is: unless I missed something "it can't be changed again"
is not actually true. A task does PR_SET_MM_EXE_FILE, then it forks
the new child. The child can do PR_SET_MM_EXE_FILE again. Is this
by design?
Oleg.