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authorEric W. Biederman <ebiederm@xmission.com>2013-11-09 04:31:29 +0400
committerEric W. Biederman <ebiederm@xmission.com>2013-11-27 08:53:58 +0400
commitf48cfddc6729ef133933062320039808bafa6f45 (patch)
tree04eb2a7f3acf504f5899521079154e5a178fafd5 /fs/dcache.c
parent0e4b0743bbe5807535ba1b0389281f9a4c1b2bb7 (diff)
downloadlinux-f48cfddc6729ef133933062320039808bafa6f45.tar.xz
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/<pid>/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 <serge.hallyn@canonical.com> Reported-by: Aditya Kali <adityakali@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c7
1 files changed, 6 insertions, 1 deletions
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();