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b=XMmkvF293u0Pe0kiXpCN0KSKP9el8rfDin08+YvXxK9dubjg35ZPnvU5agpBBaYTE /ncryhCA7ppNhpCL8zjTuawEGahS+R6IVuTFWuua/vS3zNAjzPvhwyr7P5Y5Al9iQZ 4zTfx7NlZyvVeCNpgvhpcLInRQFtHN2zQZuC4Jgw= Date: Mon, 26 Oct 2026 09:04:21 -0700 From: Andrew Morton To: "Uladzislau Rezki (Sony)" Cc: linux-mm@kvack.org, Baoquan He , LKML , "David Hildenbrand (Arm)" Subject: Re: [PATCH] mm/vmalloc: Bail out if in softirq context Message-Id: <20261026090421.e4bd83f3e20fb82852abec4e@linux-foundation.org> In-Reply-To: <20261026102503.30860-1-urezki@gmail.com> References: <20261026102503.30860-1-urezki@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) X-Archived-By: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 3589610000F X-Stat-Signature: z5ek5ux58x15mktyaqseji98sepdhcx9 X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793030663-391610 X-HE-Meta: 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 Al+B97iG 5/T/apL5t+6EmUAfG7kuUk17otQqE6U32MHVOJ8O8AUZCn9441We8wIgPszoLSOd7FU/9IZvmz8AvQQFPpyIslNKNrLd/7bW9DdJV+0gSjF4SpVCr99nbudV6jjlhlAHabBeGLyY66E6VZ2Z1CW+cIoflm6VjbCXOWwzpHVaecufPl8ugf/sLkXT4RRSXhs9N8KQTg7ua2d+zoed4Z9MQsU7rasaq6nB7I66Nbt7aoYdZTDV8/+8jC6LYyJAzLDnmaJhNa1w8SCYqZHXbiHJf8I9Qv93emfsJLV7/ 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 Mon, 26 Oct 2026 11:25:03 +0100 "Uladzislau Rezki (Sony)" wrote: > vmalloc() is not allowed to be invoked from the NMI, > hard-irq and softirq contexts because doing so may > deadlock on internal locks. > > Commit 04aa71da5f35 ("mm/vmalloc: do not trigger BUG() > on BH disabled context") replaced the deprecated in_interrupt() > macro with explicit in_nmi() and in_hardirq() checks, but > unintentionally dropped the softirq context check. > > Example: > > > vzalloc() in a task > spin_lock(&vn->busy.lock) > <------ Hard irq > irq_exit() > process softirq on the same CPU > vmalloc() > spin_lock(&vn->busy.lock) > spins forever > > > Restore the check by checking the caller's context with > the in_serving_softirq() helper. Note that, it is still > allowed to invoke vmalloc() with disabled bottom halves. > > Replace BUG_ON() with WARN_ON_ONCE() for in_nmi() and > in_hardirq() case. > > Cc: David Hildenbrand (Arm) > Fixes: 04aa71da5f35 ("mm/vmalloc: do not trigger BUG() on BH disabled context") Sounds like a cc:stable is needed? > Signed-off-by: Uladzislau Rezki (Sony) > --- > mm/vmalloc.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 7521b9b3bfd2..36e6e3be6ba4 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3252,7 +3252,13 @@ struct vm_struct *__get_vm_area_node(unsigned long size, > struct vm_struct *area; > unsigned long requested_size = size; > > - BUG_ON(in_nmi() || in_hardirq()); > + /* IRQ re-entrancy -> irq_exit() -> process softirq. */ > + if (in_serving_softirq()) > + return NULL; > + > + if (WARN_ON_ONCE(in_nmi() || in_hardirq())) > + return NULL; WARN does a lot of stuff and I rather doubt that it's all nmi-safe. I don't think this matters much - it'll probably work out and as long as *something* gets printed, it did its job. > size = ALIGN(size, 1ul << shift); > if (unlikely(!size)) > return NULL; > -- > 2.47.3