From f48cfddc6729ef133933062320039808bafa6f45 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Fri, 8 Nov 2013 16:31:29 -0800 Subject: vfs: In d_path don't call d_dname on a mount point Aditya Kali (adityakali@google.com) wrote: > Commit bf056bfa80596a5d14b26b17276a56a0dcb080e5: > "proc: Fix the namespace inode permission checks." converted > the namespace files into symlinks. The same commit changed > the way namespace bind mounts appear in /proc/mounts: > $ mount --bind /proc/self/ns/ipc /mnt/ipc > Originally: > $ cat /proc/mounts | grep ipc > proc /mnt/ipc proc rw,nosuid,nodev,noexec 0 0 > > After commit bf056bfa80596a5d14b26b17276a56a0dcb080e5: > $ cat /proc/mounts | grep ipc > proc ipc:[4026531839] proc rw,nosuid,nodev,noexec 0 0 > > This breaks userspace which expects the 2nd field in > /proc/mounts to be a valid path. The symlink /proc//ns/{ipc,mnt,net,pid,user,uts} point to dentries allocated with d_alloc_pseudo that we can mount, and that have interesting names printed out with d_dname. When these files are bind mounted /proc/mounts is not currently displaying the mount point correctly because d_dname is called instead of just displaying the path where the file is mounted. Solve this by adding an explicit check to distinguish mounted pseudo inodes and unmounted pseudo inodes. Unmounted pseudo inodes always use mount of their filesstem as the mnt_root in their path making these two cases easy to distinguish. CC: stable@vger.kernel.org Acked-by: Serge Hallyn Reported-by: Aditya Kali Signed-off-by: "Eric W. Biederman" --- fs/dcache.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 4bdb300b16e2..f7282ebf1a37 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -3061,8 +3061,13 @@ char *d_path(const struct path *path, char *buf, int buflen) * thus don't need to be hashed. They also don't need a name until a * user wants to identify the object in /proc/pid/fd/. The little hack * below allows us to generate a name for these objects on demand: + * + * Some pseudo inodes are mountable. When they are mounted + * path->dentry == path->mnt->mnt_root. In that case don't call d_dname + * and instead have d_path return the mounted path. */ - if (path->dentry->d_op && path->dentry->d_op->d_dname) + if (path->dentry->d_op && path->dentry->d_op->d_dname && + (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root)) return path->dentry->d_op->d_dname(path->dentry, buf, buflen); rcu_read_lock(); -- cgit v1.2.3 From 41301ae78a99ead04ea42672a1ab72c6f44cc81d Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 14 Nov 2013 21:22:25 -0800 Subject: vfs: Fix a regression in mounting proc Gao feng reported that commit e51db73532955dc5eaba4235e62b74b460709d5b userns: Better restrictions on when proc and sysfs can be mounted caused a regression on mounting a new instance of proc in a mount namespace created with user namespace privileges, when binfmt_misc is mounted on /proc/sys/fs/binfmt_misc. This is an unintended regression caused by the absolutely bogus empty directory check in fs_fully_visible. The check fs_fully_visible replaced didn't even bother to attempt to verify proc was fully visible and hiding proc files with any kind of mount is rare. So for now fix the userspace regression by allowing directory with nlink == 1 as /proc/sys/fs/binfmt_misc has. I will have a better patch but it is not stable material, or last minute kernel material. So it will have to wait. Cc: stable@vger.kernel.org Acked-by: Serge Hallyn Acked-by: Gao feng Tested-by: Gao feng Signed-off-by: "Eric W. Biederman" --- fs/namespace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/namespace.c b/fs/namespace.c index ac2ce8a766e1..be32ebccdeb1 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2886,7 +2886,7 @@ bool fs_fully_visible(struct file_system_type *type) struct inode *inode = child->mnt_mountpoint->d_inode; if (!S_ISDIR(inode->i_mode)) goto next; - if (inode->i_nlink != 2) + if (inode->i_nlink > 2) goto next; } visible = true; -- cgit v1.2.3