On Tue, Jan 09, 2018 at 02:23:32PM -0800, Kees Cook wrote:
On Sun, Jan 7, 2018 at 9:35 PM, Eric Biggers ebiggers3@gmail.com wrote:
From: Eric Biggers ebiggers@google.com
pipe-user-pages-hard and pipe-user-pages-soft are only supposed to apply to unprivileged users, as documented in both Documentation/sysctl/fs.txt and the pipe(7) man page.
However, the capabilities are actually only checked when increasing a pipe's size using F_SETPIPE_SZ, not when creating a new pipe. Therefore, if pipe-user-pages-hard has been set, the root user can run into it and be unable to create pipes. Similarly, if pipe-user-pages-soft has been set, the root user can run into it and have their pipes limited to 1 page each.
Fix this by allowing the privileged override in both cases.
Should this be controlled per-namespace instead of via init-ns caps?
I don't think so. Users shouldn't be able to bypass the limits by creating a user namespace.
Eric