On Tue, Dec 06, 2011 at 03:45:15PM -0800, Linus Torvalds wrote: > How about this change: > - don't change 'root' (and mark it const) > - if we hit the expected root, we're all happy and do what we do now > - if we hit some *unexpected* root (the "global root") add a '?' or > something at the head of the path. > > End result: callers like getcwd() can trivially replace their current > "path_equal(&tmp,&root)" (or whatever they do) with just checking the > first character of the end result. A good path always starts with '/'. You get broken /proc/self/mountinfo for chrooted processes with that patch. You also get /proc/mounts contents change for the same. Moreover, while we _probably_ can get away with that "prepend '?'", we'll need to make sure that all checks are comparing with '?', _not_ with '/', or you'll get nasty surprises when __d_path() gets called on e.g. pipe dentry (pipe:[...]). And while we are at it, we'd better document that "->d_dname() should never use '?' as the first character" restriction we've got. I don't know... playing with magical substrings in what it returns is, IMO, a bad idea. I really wonder if we'd be better off with just this: __d_path(path, root, buf, buflen) - expects non-NULL in root->mnt, never changes root, returns NULL if path is not under root d_absolute_path(path, ancestor, buf, buflen) - grabs the reference to the most remote ancestor it can find, puts pathname into buf, never returns NULL. Let tomoyo use that one and path_put(ancestor) afterwards (or look at it first, if it cares). And let apparmor do the following: * first call __d_path(), unless asked not to. If it returns non-NULL, great we've got that path, game over. Otherwise call d_absolute_path() and log that partial pathname, check where we'd got, etc. Just remember to path_put(ancestor) after that. We are trying to shove two different things in one function and result is ugly; so let's just split it instead of trying to breed weird hybrids. Comments? -- 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
