Re: [PATCH -next 3/3] cifsd: check return value of ksmbd_vfs_getcasexattr() correctly

From: Hyunchul Lee <hyc.lee@gmail.com>
To: Yang Yingliang <yangyingliang@huawei.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-cifsd-devel <linux-cifsd-devel@lists.sourceforge.net>,
	linux-cifs <linux-cifs@vger.kernel.org>,
	Namjae Jeon <namjae.jeon@samsung.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steve French <sfrench@samba.org>
Subject: Re: [PATCH -next 3/3] cifsd: check return value of ksmbd_vfs_getcasexattr() correctly
Date: Sat, 29 May 2021 23:13:01 +0900	[thread overview]
Message-ID: <CANFS6bYGp0CsdjovHxpaxbYVq72U3EY8C-oSphHDUSrwLmxCOA@mail.gmail.com> (raw)
In-Reply-To: <20210529082058.3012233-3-yangyingliang@huawei.com>

Hi Yang,

2021년 5월 29일 (토) 오후 5:16, Yang Yingliang <yangyingliang@huawei.com>님이 작성:
>
> If ksmbd_vfs_getcasexattr() returns -ENOMEM, stream_buf is NULL,
> it will cause null-ptr-deref when using it to copy memory. So we
> need check the return value of ksmbd_vfs_getcasexattr() by comparing
> with 0.
>
> Fixes: f44158485826 ("cifsd: add file operations")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>  fs/cifsd/vfs.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/fs/cifsd/vfs.c b/fs/cifsd/vfs.c
> index 97d5584ec870..45ba30f1f2d2 100644
> --- a/fs/cifsd/vfs.c
> +++ b/fs/cifsd/vfs.c
> @@ -274,7 +274,6 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
>  {
>         ssize_t v_len;
>         char *stream_buf = NULL;
> -       int err;
>
>         ksmbd_debug(VFS, "read stream data pos : %llu, count : %zd\n",
>                     *pos, count);
> @@ -283,10 +282,9 @@ static int ksmbd_vfs_stream_read(struct ksmbd_file *fp, char *buf, loff_t *pos,
>                                        fp->stream.name,
>                                        fp->stream.size,
>                                        &stream_buf);
> -       if (v_len == -ENOENT) {
> +       if ((int)v_len < 0) {

because ksmbd_vfs_getcasexattr can return 0, 0 has to be handled.

Thanks,
Hyunchul

>                 ksmbd_err("not found stream in xattr : %zd\n", v_len);
> -               err = -ENOENT;
> -               return err;
> +               return (int)v_len;
>         }
>
>         memcpy(buf, &stream_buf[*pos], count);
> @@ -415,9 +413,9 @@ static int ksmbd_vfs_stream_write(struct ksmbd_file *fp, char *buf, loff_t *pos,
>                                        fp->stream.name,
>                                        fp->stream.size,
>                                        &stream_buf);
> -       if (v_len == -ENOENT) {
> +       if ((int)v_len < 0) {
>                 ksmbd_err("not found stream in xattr : %zd\n", v_len);
> -               err = -ENOENT;
> +               err = (int)v_len;
>                 goto out;
>         }
>
> --
> 2.25.1
>