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([141.164.41.4]) by smtp.gmail.com with ESMTPSA id x3sm177860pgx.8.2021.06.09.08.25.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 08:25:14 -0700 (PDT) From: Changbin Du To: Alexander Viro Cc: "David S. Miller" , Jakub Kici nski , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Changbin Du , Cong Wang , David Laight , Christian Brauner Subject: [PATCH v2] nsfs: warn if ns->ops is not provided Date: Wed, 9 Jun 2021 23:25:00 +0800 Message-Id: <20210609152500.28104-1-changbin.du@gmail.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org We should not create inode for disabled namespace. A disabled namespace sets its ns->ops to NULL. Kernel could panic if we try to create a inode for such namespace. Here is an example oops in socket ioctl cmd SIOCGSKNS when NET_NS is disabled. Kernel panicked wherever nsfs trys to access ns->ops since the proc_ns_operations is not implemented in this case. [7.670023] Unable to handle kernel NULL pointer dereference at virtual address 00000010 [7.670268] pgd = 32b54000 [7.670544] [00000010] *pgd=00000000 [7.671861] Internal error: Oops: 5 [#1] SMP ARM [7.672315] Modules linked in: [7.672918] CPU: 0 PID: 1 Comm: systemd Not tainted 5.13.0-rc3-00375-g6799d4f2da49 #16 [7.673309] Hardware name: Generic DT based system [7.673642] PC is at nsfs_evict+0x24/0x30 [7.674486] LR is at clear_inode+0x20/0x9c So let's print a warning for such unexpected request which to create the nsfs inode. The issue in networking will be fixed in another change. Signed-off-by: Changbin Du Cc: Cong Wang Cc: Jakub Kicinski Cc: David Laight Cc: Christian Brauner --- fs/nsfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/nsfs.c b/fs/nsfs.c index 800c1d0eb0d0..a132827bddd5 100644 --- a/fs/nsfs.c +++ b/fs/nsfs.c @@ -62,6 +62,9 @@ static int __ns_get_path(struct path *path, struct ns_common *ns) struct inode *inode; unsigned long d; + if (WARN_ON_ONCE(!ns->ops)) + return -EINVAL; + rcu_read_lock(); d = atomic_long_read(&ns->stashed); if (!d)