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

To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm: module_alloc: check if size is 0
From: Veli-Pekka Peltola <veli-pekka.peltola@bluegiga.com>
Date: Mon, 19 Mar 2012 17:36:00 +0200
Cc: linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, Russell King <linux@arm.linux.org.uk>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org
In-reply-to: <1331125768-25454-1-git-send-email-veli-pekka.peltola@bluegiga.com>
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Hi,

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<veli-pekka.peltola@bluegiga.com>
Cc: Russell King<linux@arm.linux.org.uk>
Cc: Thomas Gleixner<tglx@linutronix.de>
Cc: Ingo Molnar<mingo@redhat.com>
Cc: "H. Peter Anvin"<hpa@zytor.com>
Cc: x86@kernel.org
---
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,
                                __builtin_return_address(0));
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);
  #ifdef MODULE_START
  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,
                                __builtin_return_address(0));
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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