linux-kernel - Re: [PATCH] ntfs3: align struct ATTR_LIST

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Message-ID: <926cddcc-2604-4d88-b9c9-91ad1d148c6c@infradead.org>
Date:   Thu, 7 Dec 2023 16:37:26 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Arnd Bergmann <arnd@...nel.org>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
Cc:     Arnd Bergmann <arnd@...db.de>, ntfs3@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ntfs3: align struct ATTR_LIST_ENTRY



On 12/7/23 06:28, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.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@...db.de>


Acked-by: Randy Dunlap <rdunlap@...radead.org>
Tested-by: Randy Dunlap <rdunlap@...radead.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