[PATCH] ntfs3: align struct ATTR_LIST_ENTRY

[PATCH] ntfs3: align struct ATTR_LIST_ENTRY

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

On architectures like i386 that don't enforce natural alignment of u64
struct members, so the recent change to remove the final 48 bits
reduced the structure size from 32 to 28 bytes:

include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct ATTR_LIST_ENTRY) == 0x20"
fs/ntfs3/ntfs.h:530:1: note: in expansion of macro 'static_assert'
  530 | static_assert(sizeof(struct ATTR_LIST_ENTRY) == 0x20);
      | ^~~~~~~~~~~~~

Add an alignment attribute that makes the structure the same across
all architectures again.

Fixes: d155617006eb ("fs/ntfs3: Fix detected field-spanning write (size 8) of single field "le->name"")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 fs/ntfs3/ntfs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ntfs3/ntfs.h b/fs/ntfs3/ntfs.h
index c8981429c721..2d409ac94cbb 100644
--- a/fs/ntfs3/ntfs.h
+++ b/fs/ntfs3/ntfs.h
@@ -525,7 +525,7 @@ struct ATTR_LIST_ENTRY {
 	__le16 id;		// 0x18: struct ATTRIB ID.
 	__le16 name[];		// 0x1A: To get real name use name_off.
 
-}; // sizeof(0x20)
+} __aligned((8)); // sizeof(0x20)
 
 static_assert(sizeof(struct ATTR_LIST_ENTRY) == 0x20);
 
-- 
2.39.2

Re: [PATCH] ntfs3: align struct ATTR_LIST_ENTRY

[Randy Dunlap]

On 12/7/23 06:28, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> On architectures like i386 that don't enforce natural alignment of u64
> struct members, so the recent change to remove the final 48 bits
> reduced the structure size from 32 to 28 bytes:
> 
> include/linux/build_bug.h:78:41: error: static assertion failed: "sizeof(struct ATTR_LIST_ENTRY) == 0x20"
> fs/ntfs3/ntfs.h:530:1: note: in expansion of macro 'static_assert'
>   530 | static_assert(sizeof(struct ATTR_LIST_ENTRY) == 0x20);
>       | ^~~~~~~~~~~~~
> 
> Add an alignment attribute that makes the structure the same across
> all architectures again.
> 
> Fixes: d155617006eb ("fs/ntfs3: Fix detected field-spanning write (size 8) of single field "le->name"")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

Thanks.

> ---
>  fs/ntfs3/ntfs.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ntfs3/ntfs.h b/fs/ntfs3/ntfs.h
> index c8981429c721..2d409ac94cbb 100644
> --- a/fs/ntfs3/ntfs.h
> +++ b/fs/ntfs3/ntfs.h
> @@ -525,7 +525,7 @@ struct ATTR_LIST_ENTRY {
>  	__le16 id;		// 0x18: struct ATTRIB ID.
>  	__le16 name[];		// 0x1A: To get real name use name_off.
>  
> -}; // sizeof(0x20)
> +} __aligned((8)); // sizeof(0x20)
>  
>  static_assert(sizeof(struct ATTR_LIST_ENTRY) == 0x20);
>  

-- 
~Randy