Messages in this thread | | | Date | Sat, 1 Jul 2023 08:24:15 +0200 | From | Christian Brauner <> | Subject | Re: [PATCH v2] pid: Replace struct pid 1-element array with flex-array |
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On Fri, Jun 30, 2023 at 11:04:22AM -0700, Kees Cook wrote: > For pid namespaces, struct pid uses a dynamically sized array member, > "numbers". This was implemented using the ancient 1-element fake flexible > array, which has been deprecated for decades. Replace it with a C99 > flexible array, refactor the array size calculations to use struct_size(), > and address elements via indexes. Note that the static initializer (which > defines a single element) works as-is, and requires no special handling. > > Without this, CONFIG_UBSAN_BOUNDS (and potentially CONFIG_FORTIFY_SOURCE) > will trigger bounds checks when entering a pid namespace: > https://lore.kernel.org/lkml/20230517-bushaltestelle-super-e223978c1ba6@brauner > > For example: unshare --fork --pid --mount-proc readlink /proc/self > > Cc: Christian Brauner <brauner@kernel.org> > Cc: Jan Kara <jack@suse.cz> > Cc: Andreas Gruenbacher <agruenba@redhat.com> > Cc: Daniel Verkamp <dverkamp@chromium.org> > Cc: "Paul E. McKenney" <paulmck@kernel.org> > Cc: Jeff Xu <jeffxu@google.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Luis Chamberlain <mcgrof@kernel.org> > Cc: Frederic Weisbecker <frederic@kernel.org> > Reported-by: syzbot+ac3b41786a2d0565b6d5@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/lkml/000000000000c6de2a05fbdecbbb@google.com/ > Acked-by: Jeff Xu <jeffxu@google.com> > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > v2: > - drop pointer math to array index conversions (torvalds) > - use struct_size_t now that it exists (torvalds) > - updated commit log with reproducer example
Thanks for that. Linus already merged the other version I gave him with his requested changes but without your struct_size_t() update. It didn't exist when you originally sent that patch afaiu and I just realized that it existed right now. In any case, I'm just going to send a trivial follow-up patch switching the two places to struct_size_t().
Thanks, Kees!
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