linux-kernel - Re: [PATCH] Fix range checks in kernfs_get_target

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Date:   Sat, 7 Jul 2018 09:56:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Bernd Edlinger <bernd.edlinger@...mail.de>
Cc:     Tejun Heo <tj@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix range checks in kernfs_get_target_path

On Fri, Jul 06, 2018 at 09:08:49PM +0000, Bernd Edlinger wrote:
> The strncpy causes a warning [-Wstringop-truncation] here,
> which indicates that it never appends a NUL byte to the path.
> The NUL byte is only there because the buffer is allocated
> with kzalloc(PAGE_SIZE, GFP_KERNEL), but since the range-check
> is also off-by-one, and PAGE_SIZE==PATH_MAX the returned string
> will not be zero-terminated if it is exactly PATH_MAX characters.
> Furthermore also the initial loop may theoretically exceed PATH_MAX
> and cause a fault.
> 
> Signed-off-by: Bernd Edlinger <bernd.edlinger@...mail.de>
> ---
>   fs/kernfs/symlink.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c
> index 08ccabd..c8b7d44a 100644
> --- a/fs/kernfs/symlink.c
> +++ b/fs/kernfs/symlink.c
> @@ -63,7 +63,10 @@ static int kernfs_get_target_path(struct kernfs_node 
> *parent,

Your patch is line-wrapped and can not be applied :(