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From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Date: Tue, 16 Apr 2024 01:44:59 +0900
Message-ID: <CAKFNMon3DWhBxMor7UNqTcrTdms6nUQF+=uWDeEc0wWerH4sOQ@mail.gmail.com>
Subject: Re: [PATCH] nilfs: Fix OOB in nilfs_set_de_type
To: Jeongjun Park <aha310510@gmail.com>
Cc: linux-nilfs@vger.kernel.org, linux-kernel@vger.kernel.org, 
	syzbot+2e22057de05b9f3b30d8@syzkaller.appspotmail.com
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On Tue, Apr 16, 2024 at 12:40=E2=80=AFAM Jeongjun Park  wrote:
>
>
> static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *i=
node)
> {
>         umode_t mode =3D inode->i_mode;
>
>         de->file_type =3D nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT]; /=
/ oob
> }
>
>
>
> The size of the nilfs_type_by_mode array in the fs/nilfs2/dir.c file is d=
efined
> as "S_IFMT >> S_SHIFT", but the nilfs_set_de_type() function, which uses =
this array,
> specifies the index to read from the array in the same way as "(mode & S_=
IFMT) >> S_SHIFT".
>
> However, when the index is determined this way, an out-of-bounds (OOB) er=
ror occurs by referring
> to an index that is 1 larger than the array size when the condition "mode=
 & S_IFMT =3D=3D S_IFMT" is satisfied.
> Therefore, a patch to resize the nilfs_type_by_mode array should be appli=
ed to prevent OOB errors.
>
>
>
> Reported-and-tested-by: syzbot+2e22057de05b9f3b30d8@syzkaller.appspotmail=
com
> Fixes: 2ba466d74ed7 ("nilfs2: directory entry operations")
> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> ---
>  fs/nilfs2/dir.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
> index bc846b904b68..aee40db7a036 100644
> --- a/fs/nilfs2/dir.c
> +++ b/fs/nilfs2/dir.c
> @@ -240,7 +240,7 @@ nilfs_filetype_table[NILFS_FT_MAX] =3D {
>
>  #define S_SHIFT 12
>  static unsigned char
> -nilfs_type_by_mode[S_IFMT >> S_SHIFT] =3D {
> +nilfs_type_by_mode[(S_IFMT >> S_SHIFT) + 1] =3D {
>         [S_IFREG >> S_SHIFT]    =3D NILFS_FT_REG_FILE,
>         [S_IFDIR >> S_SHIFT]    =3D NILFS_FT_DIR,
>         [S_IFCHR >> S_SHIFT]    =3D NILFS_FT_CHRDEV,

Thank you for your prompt response and posting the patch.

A little formatting and tag editing is required, but it's okay.
I'll handle this patch.

Thanks,
Ryusuke Konishi