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Re: [PATCH v2] mm: module_alloc: check if size is 0

Subject: Re: [PATCH v2] mm: module_alloc: check if size is 0
From: Veli-Pekka Peltola <>
Date: Mon, 19 Mar 2012 17:36:00 +0200
Cc:,, Russell King <>, Thomas Gleixner <>, Ingo Molnar <>, "H. Peter Anvin" <>,
In-reply-to: <>
References: <> <>
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On 03/07/2012 03:09 PM, Veli-Pekka Peltola wrote:
After commit de7d2b567d040e3b67fe7121945982f14343213d (mm/vmalloc.c: report
more vmalloc failures) users will get a warning if vmalloc_node_range() is
called with size 0. This happens if module's init size equals to 0. This
patch changes ARM, MIPS and x86 module_alloc() to return NULL before calling
vmalloc_node_range() that would also return NULL and print a warning.

Signed-off-by: Veli-Pekka Peltola<>
Cc: Russell King<>
Cc: Thomas Gleixner<>
Cc: Ingo Molnar<>
Cc: "H. Peter Anvin"<>
I found this with ARM but after checking out various implementations of
module_alloc() I thought it would be better to fix all at once.

One way to replicate the warning:
compile kernel with CONFIG_KALLSYMS=n
insmod a module without init, I used usb-common.ko

Changes since v1:
  - changed style as hpa suggested

  arch/arm/kernel/module.c  |    2 ++
  arch/mips/kernel/module.c |    2 ++
  arch/x86/kernel/module.c  |    2 +-
  3 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index 1e9be5d..17648e2 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -39,6 +39,8 @@
  #ifdef CONFIG_MMU
  void *module_alloc(unsigned long size)
+       if (!size)
+               return NULL;
        return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
                                GFP_KERNEL, PAGE_KERNEL_EXEC, -1,
diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
index a5066b1..1a51de1 100644
--- a/arch/mips/kernel/module.c
+++ b/arch/mips/kernel/module.c
@@ -47,6 +47,8 @@ static DEFINE_SPINLOCK(dbe_lock);
  void *module_alloc(unsigned long size)
+       if (!size)
+               return NULL;
        return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
                                GFP_KERNEL, PAGE_KERNEL, -1,
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 925179f..fd44d69 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -38,7 +38,7 @@

  void *module_alloc(unsigned long size)
-       if (PAGE_ALIGN(size)>  MODULES_LEN)
+       if (!size || PAGE_ALIGN(size)>  MODULES_LEN)
                return NULL;
        return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
                                GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,

Any comments on this? Should I split all architectures to separate patches?

I just tested 3.3 on ARM and x86, both printed a warning and call trace without this patch.

Veli-Pekka Peltola

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