linux-kernel - Re: [PATCH] fanotify: avoid possible NULL dereference

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Message-ID: <CAOQ4uxhtZSr-kq3G1vmm4=GyBO3E5RdSbGSp108moRiRBx4vvg@mail.gmail.com>
Date:   Thu, 10 Aug 2023 20:58:16 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Su Hui <suhui@...china.com>
Cc:     jack@...e.cz, repnop@...gle.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] fanotify: avoid possible NULL dereference

On Tue, Aug 8, 2023 at 12:19 PM Su Hui <suhui@...china.com> wrote:
>
> smatch error:
> fs/notify/fanotify/fanotify_user.c:462 copy_fid_info_to_user():
> we previously assumed 'fh' could be null (see line 421)
>
> Fixes: afc894c784c8 ("fanotify: Store fanotify handles differently")
> Signed-off-by: Su Hui <suhui@...china.com>'

Reviewed-by: Amir Goldstein <amir73il@...il.com>

> ---
>  fs/notify/fanotify/fanotify_user.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index f69c451018e3..5a5487ae2460 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -459,12 +459,13 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
>         if (WARN_ON_ONCE(len < sizeof(handle)))
>                 return -EFAULT;
>
> -       handle.handle_type = fh->type;
>         handle.handle_bytes = fh_len;
>
>         /* Mangle handle_type for bad file_handle */
>         if (!fh_len)
>                 handle.handle_type = FILEID_INVALID;
> +       else
> +               handle.handle_type = fh->type;
>
>         if (copy_to_user(buf, &handle, sizeof(handle)))
>                 return -EFAULT;
> --
> 2.30.2
>