On Mon, Sep 23, 2024 at 05:31:47PM +0300, Jarkko Sakkinen wrote: > On Mon Sep 23, 2024 at 12:26 PM EEST, Herbert Xu wrote: > > > + > > > > + err = rng->read(rng, buffer, size, wait); > > > > + if (WARN_ON_ONCE(err > 0 && err > size)) > > > > > > Are you sure you want to use WARN_ON_ONCE here instead of > > > pr_warn_once()? I.e. is it worth of taking down the whole > > > kernel? > > > > Absolutely. If this triggers it's a serious kernel bug and we > > should gather as much information as possible. pr_warn_once is > > not the same thing as WARN_ON_ONCE in terms of what it prints. > > Personally I allow the use of WARN only as the last resort. > > If you need stack printout you can always use dump_stack(). > > > > > If people want to turn WARNs into BUGs, then they've only got > > themselves to blame when the kernel goes down. On the other > > hand perhaps they *do* want this to panic and we should hand > > it to them. > > Actually when you turn on "panic_on_warn" the user expectation is and > should be that the sites where WARN is used have been hand picked with > consideration so that panic happens for a reason. > > This has also been denoted repeatedly by Greg: > > https://lore.kernel.org/linux-cve-announce/2024061828-CVE-2024-36975-6719@gregkh/ > > I should check this somewhere but actually these days a wrongly chosen > WARN() might lead to CVE entry. That fix was by me but I never created > the CVE. > > Greg, did we have something under Documentation/ that would fully > address the use of WARN? Please see: https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on which describes that. We should make it more explicit that any WARN() or WARN_ON() calls that can be hit by user interactions somehow, will end up getting a CVE id when we fix it up to not do so. thanks, greg k-h
