linux-kernel - Re: [PATCH linux-next] xfs: use strscpy() to instead of strncpy()

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Date:   Sat, 11 Feb 2023 13:06:41 +0800
From:   Long Li <leo.lilong@...wei.com>
To:     "Darrick J. Wong" <djwong@...nel.org>, <yang.yang29@....com.cn>
CC:     <linux-xfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <xu.panda@....com.cn>
Subject: Re: [PATCH linux-next] xfs: use strscpy() to instead of strncpy()

On Wed, Feb 01, 2023 at 04:57:02PM -0800, Darrick J. Wong wrote:
> On Mon, Jan 09, 2023 at 07:40:43PM +0800, yang.yang29@....com.cn wrote:
> > From: Xu Panda <xu.panda@....com.cn>
> > 
> > The implementation of strscpy() is more robust and safer.
> > That's now the recommended way to copy NUL-terminated strings.
> > 
> > Signed-off-by: Xu Panda <xu.panda@....com.cn>
> > Signed-off-by: Yang Yang <yang.yang29@....com.cn>
> 
> Looks fine,
> Reviewed-by: Darrick J. Wong <djwong@...nel.org>
> 
> --D
> 
> > ---
> >  fs/xfs/xfs_xattr.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
> > index 10aa1fd39d2b..913c1794bc2f 100644
> > --- a/fs/xfs/xfs_xattr.c
> > +++ b/fs/xfs/xfs_xattr.c
> > @@ -212,9 +212,7 @@ __xfs_xattr_put_listent(
> >  	offset = context->buffer + context->count;
> >  	memcpy(offset, prefix, prefix_len);
> >  	offset += prefix_len;
> > -	strncpy(offset, (char *)name, namelen);			/* real name */
> > -	offset += namelen;
> > -	*offset = '\0';
> > +	strscpy(offset, (char *)name, namelen + 1);			/* real name */

The name is not null terminated, it will result slab-out-of-bounds in strscpy().

[1] https://lore.kernel.org/linux-xfs/00000000000065a46a05f4529f59@google.com/T/#u

> > 
> >  compute_size:
> >  	context->count += prefix_len + namelen + 1;
> > -- 
> > 2.15.2