There were no comments at the last submission: http://lkml.org/lkml/2008/7/30/204 Andrew, could you please put this into -mm so it doesn't get lost while Al is absent? It really shoulnd't hurt. Thanks, Miklos ---- 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> --- fs/dcache.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) Index: linux-2.6/fs/dcache.c =================================================================== --- linux-2.6.orig/fs/dcache.c 2009-07-03 13:12:06.000000000 +0200 +++ linux-2.6/fs/dcache.c 2009-08-14 11:30:43.000000000 +0200 @@ -1882,6 +1882,12 @@ 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 @@ -1949,8 +1955,18 @@ 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; -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
