vfs: make mounts and mountstats honor root dir like mountinfo does

As we already show mountpoints relative to the root directory, thanks
to the change made back in 2000, change show_vfsmnt() and show_vfsstat()
to skip out-of-root mountpoints the same way as show_mountinfo() does.

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 2 deletions

diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 789e8d1e21db..0f96f71ab32b 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -91,6 +91,7 @@ static void show_type(struct seq_file *m, struct super_block *sb)
 
 static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
 {
+        struct proc_mounts *p = proc_mounts(m);
         struct mount *r = real_mount(mnt);
         int err = 0;
         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
@@ -104,7 +105,10 @@ static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
         }
         seq_putc(m, ' ');
-        seq_path(m, &mnt_path, " \t\n\\");
+        /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
+        err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
+        if (err)
+                goto out;
         seq_putc(m, ' ');
         show_type(m, sb);
         seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
@@ -181,6 +185,7 @@ out:
 
 static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
 {
+        struct proc_mounts *p = proc_mounts(m);
         struct mount *r = real_mount(mnt);
         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
         struct super_block *sb = mnt_path.dentry->d_sb;
@@ -200,7 +205,10 @@ static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
 
         /* mount point */
         seq_puts(m, " mounted on ");
-        seq_path(m, &mnt_path, " \t\n\\");
+        /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
+        err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
+        if (err)
+                goto out;
         seq_putc(m, ' ');
 
         /* file system type */
@@ -215,6 +223,7 @@ static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
         }
 
         seq_putc(m, '\n');
+out:
         return err;
 }