Hello.
On Fri, Mar 06, 2020 at 01:52:07PM +0100, Vlastimil Babka wrote:
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index e794367f681e..e77c6c1fad34 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -1118,6 +1118,8 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
> > if (write) {
> > if (down_write_killable(&mm->mmap_sem))
> > return -EINTR;
> > + if (current->mm != mm && !mmget_still_valid(mm))
> > + goto skip_mm;
>
> This will return 0, is that correct? Shoudln't there be a similar error e.g. as
> when finding the task by pid fails (-ESRCH ?), because IIUC the task here is
> going away and dumping the core?
Yeah.
Something like this then:
===
diff --git a/mm/madvise.c b/mm/madvise.c
index 48d1da08c160..7ed2f4d13924 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1122,6 +1122,10 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
if (write) {
if (down_write_killable(&mm->mmap_sem))
return -EINTR;
+ if (current->mm != mm && !mmget_still_valid(mm)) {
+ error = -ESRCH;
+ goto skip_mm;
+ }
} else {
down_read(&mm->mmap_sem);
}
@@ -1173,6 +1177,7 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
}
out:
blk_finish_plug(&plug);
+skip_mm:
if (write)
up_write(&mm->mmap_sem);
else
===
?
>
> > } else {
> > down_read(&mm->mmap_sem);
> > }
> > @@ -1169,6 +1171,7 @@ int do_madvise(struct task_struct *target_task, struct mm_struct *mm,
> > }
> > out:
> > blk_finish_plug(&plug);
> > +skip_mm:
> > if (write)
> > up_write(&mm->mmap_sem);
> > else
> >
>
--
Best regards,
Oleksandr Natalenko (post-factum)
Principal Software Maintenance Engineer
