The patch titled vfs: fix d_path() for unreachable paths has been added to the -mm tree. Its filename is vfs-fix-d_path-for-unreachable-paths.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: vfs: fix d_path() for unreachable paths From: Miklos Szeredi <mszeredi@xxxxxxx> John Johansen pointed out, that getcwd(2) will give a garbled result if a bind mount of a non-filesystem-root directory is detached: > mkdir /mnt/foo > mount --bind /etc /mnt/foo > cd /mnt/foo/skel > umount -l /mnt/foo > /bin/pwd etcskel If it was the root of the filesystem which was detached, it will give a saner looking result, but it still won't be a valid absolute path by which the CWD can be reached (assuming the process's root is not also on the detached mount). A similar issue happens if the CWD is outside the process's root or in a different namespace. These problems are relevant to symlinks under /proc/<pid>/ and /proc/<pid>/fd/ as well. This patch addresses all these issues, by prefixing such unreachable paths with "(unreachable)". This isn't perfect since the returned path may still be a valid _relative_ path, and applications may not check the result of getcwd() for starting with a '/' before using it. For this reason Andreas Gruenbacher thinks getcwd(2) should return ENOENT in these cases, but that breaks /bin/pwd and bash in the above cases. Reported-by: John Johansen <jjohansen@xxxxxxx> Cc: Matthew Wilcox <matthew@xxxxxx> Cc: Andreas Gruenbacher <agruen@xxxxxxx> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/dcache.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff -puN fs/dcache.c~vfs-fix-d_path-for-unreachable-paths fs/dcache.c --- a/fs/dcache.c~vfs-fix-d_path-for-unreachable-paths +++ a/fs/dcache.c @@ -1883,6 +1883,12 @@ static int prepend_name(char **buffer, i return prepend(buffer, buflen, name->name, name->len); } +static bool is_pseudo_root(struct dentry *dentry) +{ + return IS_ROOT(dentry) && + (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/'); +} + /** * __d_path - return the path of a dentry * @path: the dentry/vfsmount to report @@ -1950,8 +1956,18 @@ out: global_root: retval += 1; /* hit the slash */ - if (prepend_name(&retval, &buflen, &dentry->d_name) != 0) - goto Elong; + + if (is_pseudo_root(dentry)) { + /* Pseudo filesystem with "foo:" prefix */ + if (prepend_name(&retval, &buflen, &dentry->d_name) != 0) + goto Elong; + } else { + /* + * Unreachable (detached or outside root or outside namespace) + */ + if (prepend(&retval, &buflen, "(unreachable)/", 14) != 0) + goto Elong; + } root->mnt = vfsmnt; root->dentry = dentry; goto out; _ Patches currently in -mm which might be from mszeredi@xxxxxxx are linux-next.patch vfs-fix-vfs_rename_dir-for-fs_rename_does_d_move-filesystems.patch fs-remove-unneeded-dcache_unhashed-tricks.patch vfs-fix-d_path-for-unreachable-paths.patch vfs-seq_file-add-helpers-for-data-filling.patch vfs-revert-proc-mounts-to-old-behavior-for-unreachable-mountpoints.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html