smb/client: fix possible infinite loop and oob read in symlink_data()

commit 7d9a7f1 upstream.

On 32-bit architectures, the infinite loop is as follows:

  len = p->ErrorDataLength == 0xfffffff8
  u8 *next = p->ErrorContextData + len
  next == p

On 32-bit architectures, the out-of-bounds read is as follows:

  len = p->ErrorDataLength == 0xfffffff0
  u8 *next = p->ErrorContextData + len
  next == (u8 *)p - 8

Reported-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Fixes: 76894f3 ("cifs: improve symlink handling for smb2+")
Cc: stable@vger.kernel.org
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Ye Bin

fs/smb/client/smb2file.c

@@ -49,6 +49,9 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov)
 				 __func__, le32_to_cpu(p->ErrorId));
 
 			len = ALIGN(le32_to_cpu(p->ErrorDataLength), 8);
+			if (len > end - ((u8 *)p + sizeof(*p)))
+				return ERR_PTR(-EINVAL);
+
 			p = (struct smb2_error_context_rsp *)(p->ErrorContextData + len);
 		}
 	} else if (le32_to_cpu(err->ByteCount) >= sizeof(*sym) &&