O Wed, Aug 19, 2020 at 10:43:16AM -0600, Ross Zwisler wrote: > From: Mattias Nissler <mnissler@xxxxxxxxxxxx> > > For mounts that have the new "nosymfollow" option, don't follow symlinks > when resolving paths. The new option is similar in spirit to the > existing "nodev", "noexec", and "nosuid" options, as well as to the > LOOKUP_NO_SYMLINKS resolve flag in the openat2(2) syscall. Various BSD > variants have been supporting the "nosymfollow" mount option for a long > time with equivalent implementations. > > Note that symlinks may still be created on file systems mounted with > the "nosymfollow" option present. readlink() remains functional, so > user space code that is aware of symlinks can still choose to follow > them explicitly. > > Setting the "nosymfollow" mount option helps prevent privileged > writers from modifying files unintentionally in case there is an > unexpected link along the accessed path. The "nosymfollow" option is > thus useful as a defensive measure for systems that need to deal with > untrusted file systems in privileged contexts. > > More information on the history and motivation for this patch can be > found here: > > https://sites.google.com/a/chromium.org/dev/chromium-os/chromiumos-design-docs/hardening-against-malicious-stateful-data#TOC-Restricting-symlink-traversal > > Signed-off-by: Mattias Nissler <mnissler@xxxxxxxxxxxx> > Signed-off-by: Ross Zwisler <zwisler@xxxxxxxxxx> > Reviewed-by: Aleksa Sarai <cyphar@xxxxxxxxxx> > --- > Changes since v7 [1]: > * Rebased onto v5.9-rc1. > * Added selftest in second patch. > * Added Aleska's Reviewed-By tag. Thank you for the review! > > After this lands I will upstream changes to util-linux[2] and man-pages > [3]. > > [1]: https://lkml.org/lkml/2020/8/11/896 > [2]: https://github.com/rzwisler/util-linux/commit/7f8771acd85edb70d97921c026c55e1e724d4e15 > [3]: https://github.com/rzwisler/man-pages/commit/b8fe8079f64b5068940c0144586e580399a71668 > --- Friendly ping on this. Al, now that the changes to fs/namei.c have landed and we're past the merge window for v5.9, what are your thoughts on this patch and the associated test?
