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Sat, 14 Nov 2026 05:48:21 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Sat, 14 Nov 2026 14:48:18 +0100 To: Linus Torvalds Cc: Herbert Xu , Uladzislau Rezki , "Liam R. Howlett (Google)" , Davidlohr Bueso , Michal Hocko , Baoquan He , Alexander Potapenko , Andrey Ryabinin , Marco Elver , Michal Hocko , Andrew Morton , Thomas Graf , linux-mm@kvack.org, linux-kernel@vger.kernel.org, maple-tree@lists.infradead.org, Lorenzo Stoakes , Chris Mason , Alice Ryhl , Andrew Ballance , stable@vger.kernel.org, "David Hildenbrand (Arm)" Subject: Re: [PATCH] mm: kvmalloc: Bail if called with soft or hard IRQs disabled Message-ID: References: X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: B6C6EC0003 X-Rspamd-Server: rspam12 X-Stat-Signature: 6qgdh8zqy1cmoqd6au8j1fydub5c8hjy X-Rspam-User: X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1794664103-781323 X-HE-Meta: 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 V7H1dhkJ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Fri, Nov 13, 2026 at 09:47:13AM -0800, Linus Torvalds wrote: > On Fri, 13 Nov 2026 at 05:03, Herbert Xu wrote: > > > > OK let's try this patch: > > I don't think this is wrong, but I do wonder if we should at least > have *some* way to detect these cases and report them. > > Also, it turns out that in __get_vm_area_node(), we have > > BUG_ON(in_nmi() || in_hardirq()); > > so this call sequence already has a *limited* test for this all. It's > just that it explicitly allows softirqs, probably because it used that > bogus BUG_ON() pattern, so it wasn't a debug aid, it was a "the > machine is dead" > > I wish people would stop using BUG_ON() and friends. They are *only* > valid for things where "something bad happened, I can't recover". > > That __get_vm_area_node() is not such a case. That function has a > perfectly well-defined "what to do in case of errors". It already does > it for lots of other cases: just return NULL. > > So using BUG_ON() is wrong, wrong, WRONG. Commit 04aa71da5f35 > ("mm/vmalloc: do not trigger BUG() on BH disabled context") was simply > not the correct thing to do. > > The correct thing to do was to replace the buggy sh*t-for-brains > BUG_ON() with the right sequence: > > - BUG_ON(in_interrupt()); > + if (WARN_ON_ONCE(in_interrupt()) > + return NULL; > I agree with this. The vmalloc() used to BUG_ON() if in_interrupt(). The easiest is to restore the old context restriction and replace BUG_ON() with WARN_ON_ONCE() followed by returning NULL. That would not stop machine but would show invalid callers. If there are no objections i can send a patch. -- Uladzislau Rezki