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Thu, 12 Nov 2026 04:11:54 -0800 (PST) Received: from milan ([2001:9b1:d5a0:a500::24b]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6b7834cdc23sm1610428a12.12.2026.11.12.04.11.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Nov 2026 04:11:53 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 12 Nov 2026 13:11:51 +0100 To: Hao Ge Cc: Uladzislau Rezki , Dev Jain , Suren Baghdasaryan , Andrew Morton , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Dennis Zhou , Tejun Heo , Christoph Lameter , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Sashiko Subject: Re: [PATCH v4 4/9] mm/vmalloc: BUG_ON() on an unaligned range in vmap_pages_range_noflush_walk() Message-ID: References: <20261110112546.261415-1-hao.ge@linux.dev> <20261110112546.261415-5-hao.ge@linux.dev> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261110112546.261415-5-hao.ge@linux.dev> On Tue, Nov 10, 2026 at 07:25:41PM +0800, Hao Ge wrote: > The pte loop of vmap_pages_pte_range() maps whole pages and stops > only when addr lands exactly on end. An unaligned end lets addr > jump over it and the loop keeps mapping into whatever follows the > range. An unaligned start maps the page below the range with its > first pte. That corruption is impossible to debug afterwards, so > bug out on addr and end at the entry of > vmap_pages_range_noflush_walk(). > > Reported-by: Sashiko > Signed-off-by: Hao Ge > --- > mm/vmalloc.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 27f2674a5556..86fbb1d2b27a 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -698,6 +698,8 @@ static int vmap_pages_range_noflush_walk(unsigned long addr, unsigned long end, > pgtbl_mod_mask mask = 0; > > BUG_ON(addr >= end); > + BUG_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end)); > + > But why do we add this? We used to live without it and as far i see we have not gotten any report about any unaligned addresses un-maping. The vmap allocator grantees that va->va_start/end have to be page aligned. -- Uladzislau Rezki