linux-kernel - Re: [PATCH v11 18/19] module: fix types of device tables aliases

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Date:	Tue, 3 Feb 2015 15:51:45 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andrey Ryabinin <a.ryabinin@...sung.com>
Cc:	linux-kernel@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
	Konstantin Serebryany <kcc@...gle.com>,
	Dmitry Chernenkov <dmitryc@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-mm@...ck.org, Rusty Russell <rusty@...tcorp.com.au>,
	James Bottomley <James.Bottomley@...senPartnership.com>
Subject: Re: [PATCH v11 18/19] module: fix types of device tables aliases

On Tue, 03 Feb 2015 20:43:11 +0300 Andrey Ryabinin <a.ryabinin@...sung.com> wrote:

> MODULE_DEVICE_TABLE() macro used to create aliases to device tables.
> Normally alias should have the same type as aliased symbol.
> 
> Device tables are arrays, so they have 'struct type##_device_id[x]'
> types. Alias created by MODULE_DEVICE_TABLE() will have non-array type -
> 	'struct type##_device_id'.
> 
> This inconsistency confuses compiler, it could make a wrong
> assumption about variable's size which leads KASan to
> produce a false positive report about out of bounds access.
> 
> For every global variable compiler calls __asan_register_globals()
> passing information about global variable (address, size, size with
> redzone, name ...) __asan_register_globals() poison symbols
> redzone to detect possible out of bounds accesses.
> 
> When symbol has an alias __asan_register_globals() will be called
> as for symbol so for alias. Compiler determines size of variable by
> size of variable's type. Alias and symbol have the same address,
> so if alias have the wrong size part of memory that actually belongs
> to the symbol could be poisoned as redzone of alias symbol.
> 
> By fixing type of alias symbol we will fix size of it, so
> __asan_register_globals() will not poison valid memory.
> 
> ...
>
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -135,7 +135,7 @@ void trim_init_extable(struct module *m);
>  #ifdef MODULE
>  /* Creates an alias so file2alias.c can find device table. */
>  #define MODULE_DEVICE_TABLE(type, name)					\
> -  extern const struct type##_device_id __mod_##type##__##name##_device_table \
> +extern const typeof(name) __mod_##type##__##name##_device_table		\
>    __attribute__ ((unused, alias(__stringify(name))))
>  #else  /* !MODULE */
>  #define MODULE_DEVICE_TABLE(type, name)

This newly requires that `name' has been defined at the
MODULE_DEVICE_TABLE expansion site.

So drivers/scsi/be2iscsi/be_main.c explodes because we converted

extern const struct pci_device_id __mod_pci__beiscsi_pci_id_table_device_table __attribute__ ((unused, alias("beiscsi_pci_id_table")));

into

extern const typeof(beiscsi_pci_id_table) __mod_pci__beiscsi_pci_id_table_device_table __attribute__ ((unused, alias("beiscsi_pci_id_table")));

before beiscsi_pci_id_table was defined.


There are probably others, so I'll start accumulating the fixes.



From: Andrew Morton <akpm@...ux-foundation.org>
Subject: MODULE_DEVICE_TABLE: fix some callsites

The patch "module: fix types of device tables aliases" newly requires that
invokations of

MODULE_DEVICE_TABLE(type, name);

come *after* the definition of `name'.  That is reasonable, but some
drivers weren't doing this.  Fix them.

Cc: James Bottomley <James.Bottomley@...senPartnership.com>
Cc: Andrey Ryabinin <a.ryabinin@...sung.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 drivers/scsi/be2iscsi/be_main.c |    1 -
 1 file changed, 1 deletion(-)

diff -puN drivers/scsi/be2iscsi/be_main.c~module_device_table-fix-some-callsites drivers/scsi/be2iscsi/be_main.c
--- a/drivers/scsi/be2iscsi/be_main.c~module_device_table-fix-some-callsites
+++ a/drivers/scsi/be2iscsi/be_main.c
@@ -48,7 +48,6 @@ static unsigned int be_iopoll_budget = 1
 static unsigned int be_max_phys_size = 64;
 static unsigned int enable_msix = 1;
 
-MODULE_DEVICE_TABLE(pci, beiscsi_pci_id_table);
 MODULE_DESCRIPTION(DRV_DESC " " BUILD_STR);
 MODULE_VERSION(BUILD_STR);
 MODULE_AUTHOR("Emulex Corporation");
_

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