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? BR, Jarkko
