mm: make apply_to_page_range more robust

PATCH Superseded Mika Penttilä 3 participants 3 messages Jan 15, 2016 – Jan 19, 2016

Subsystems (2)

Memory management MM core

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Mika Penttilä

author

2016-01-15 05:41 UTC #0 lore raw

PATCH 1/1 mm: make apply_to_page_range more robust

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 [email protected]

---

mm/memory.c +0 -0

index c387430..c3d1a2e 100644
@@ -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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Pekka Enberg

Reviewed-by on v1 1/1

2016-01-17 10:02 UTC #1 lore raw

Quoted 6 lines · Mika Penttilä

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);

Quoted 7 lines

can be 0 triggering the bug BUG_ON(addr >= end);.
Fix by letting call with zero size succeed.
--Mika
Signed-off-by [email protected]

Reviewed-by Pekka Enberg <[email protected]>

We could also replace that BUG_ON() with a WARN_ON() and return -EINVAL.

Quoted 18 lines

---

mm/memory.c +3 -0

index c387430..c3d1a2e 100644
@@ -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 {

Quoted 5 lines

--
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David Rientjes

2016-01-19 22:21 UTC #2 lore raw

In reply to Mika Penttilä

Quoted 29 lines · Mika PenttilA?

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 [email protected]
---
mm/memory.c +3 -0
index c387430..c3d1a2e 100644
@@ -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);

Quoted 1 line

        do {

What is calling apply_to_page_range() with size == 0? I'm not sure we should be adding "robust"ness here and that size == 0 is actually an indication of a bug somewhere else that we want to know about.

Btw, your patch is line-wrapped and your sign-off-line doesn't include your full name.