[PATCH] mm: make apply_to_page_range more robust

[Mika Penttilä <mika.penttila@xxxxxxxxxxxx>]

Recent changes (4.4.0+) in module loader triggered oops on ARM. While
loading a module, size in :

apply_to_page_range(struct mm_struct *mm, unsigned long addr,   unsigned
long size, pte_fn_t fn, void *data);

can be 0 triggering the bug  BUG_ON(addr >= end);.

Fix by letting call with zero size succeed.

--Mika

Signed-off-by: mika.penttila@xxxxxxxxxxxx
---

diff --git a/mm/memory.c b/mm/memory.c
index c387430..c3d1a2e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1884,6 +1884,9 @@ int apply_to_page_range(struct mm_struct *mm,
unsigned long addr,
        unsigned long end = addr + size;
        int err;

+       if (!size)
+               return 0;
+
        BUG_ON(addr >= end);
        pgd = pgd_offset(mm, addr);
        do {

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