On Sun, Apr 1, 2012 at 15:03, H. Peter Anvin <hpa@xxxxxxxxx> wrote: > On 04/01/2012 05:57 AM, Alexey Dobriyan wrote: >> * /proc/self/fd is unreliable: >> proc may be unconfigured or not mounted at expected place. >> Looking at /proc/self/fd requires opening directory >> which may not be available due to malicious rlimit drop or ENOMEM situations. >> Not opening directory is equivalent to dumb close(2) loop except slower. > > This is really the motivation for this... the real question is how much > functionality is actually available in the system without /proc mounted, > and in particular if this particular subcase is worth optimizing ... > after all, if someone is maliciously setting rlimit, we can just abort > (if someone can set an rlimit they can also force an abort) or revert to > the slow path. Well, I imagine one typical usecase for closing all FDs is for security isolation purposes (EG: chroot()+etc), and in a great deal of chroot environments you don't have /proc available. In particular /proc has been a source of a lot of privilege escalations in the past, so avoiding mounting it in a chroot is good security policy if possible. Cheers, Kyle Moffett -- 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
