mm: respect arch_dup_mmap() return value

Commit d70f2a1 ("include/linux/sched/mm.h: uninline mmdrop_async(),
etc") ignored the return value of arch_dup_mmap(). As a result, on x86,
a failure to duplicate the LDT (e.g. due to memory allocation error)
would leave the duplicated memory mapping in an inconsistent state.

Fix by using the return value, as it was before the change.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: d70f2a1 ("include/linux/sched/mm.h: uninline mmdrop_async(), etc")
Signed-off-by: Nadav Amit <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: <[email protected]>

Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/fork.c

@@ -550,8 +550,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 			goto out;
 	}
 	/* a new mm has just been created */
-	arch_dup_mmap(oldmm, mm);
-	retval = 0;
+	retval = arch_dup_mmap(oldmm, mm);
 out:
 	up_write(&mm->mmap_sem);
 	flush_tlb_mm(oldmm);