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[87.10.127.160]) by smtp.gmail.com with ESMTPSA id z17-20020aa7cf91000000b004c2158e87e6sm1656646edx.97.2023.05.21.01.28.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 May 2023 01:28:16 -0700 (PDT) From: Andrea Righi To: Miklos Szeredi Cc: Amir Goldstein , linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 0/3] overlayfs: debugging check for valid superblock Date: Sun, 21 May 2023 10:28:10 +0200 Message-Id: <20230521082813.17025-1-andrea.righi@canonical.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1766493556428908523?= X-GMAIL-MSGID: =?utf-8?q?1766493556428908523?= OVL_FS() is used to get a struct ovl_fs from a sturct super_block, but we don't have any check to determine if the superblock is valid or not. This can lead to unexpected behaviors or bugs that are pretty hard to track down. Add an explicit WARN_ON_ONCE() check to OVL_FS() to make sure it's always used with a valid overlayfs superblock. To avoid enabling this additional pendatic check everywhere, introduce the new config option CONFIG_OVERLAY_FS_DEBUG, that can be used in the future also for other additional debugging checks. Maybe a nicer solution could be to return an error from OVL_FS() when it's used with an invalid superblock and propagate the error in the rest of overlayfs code, but for now having at least the possibility to trigger a warning can help to catch potential bugs in advance. Changelog (v2 -> v3): - do not hide is_ovl_fs_sb() under CONFIG_OVERLAY_FS_DEBUG - split consistent use of OVL_FS() and superblock validation in two separate patches Changelog (v1 -> v2): - replace BUG_ON() with WARN_ON_ONCE() - introduce CONFIG_OVERLAY_FS_DEBUG Andrea Righi (3): ovl: Kconfig: introduce CONFIG_OVERLAY_FS_DEBUG ovl: make consistent use of OVL_FS() ovl: validate superblock in OVL_FS() fs/overlayfs/Kconfig | 9 +++++++++ fs/overlayfs/copy_up.c | 2 +- fs/overlayfs/export.c | 10 +++++----- fs/overlayfs/inode.c | 8 ++++---- fs/overlayfs/namei.c | 2 +- fs/overlayfs/ovl_entry.h | 14 ++++++++++++++ fs/overlayfs/super.c | 12 ++++++------ fs/overlayfs/util.c | 18 +++++++++--------- 8 files changed, 49 insertions(+), 26 deletions(-)