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Thu, 12 Nov 2026 04:15:04 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Thu, 12 Nov 2026 13:15:01 +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 Subject: Re: [PATCH v4 5/9] mm/vmalloc: BUG_ON() on an unaligned range in __vunmap_range_noflush() Message-ID: References: <20261110112546.261415-1-hao.ge@linux.dev> <20261110112546.261415-6-hao.ge@linux.dev> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261110112546.261415-6-hao.ge@linux.dev> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 9F1064000A X-Stat-Signature: abizj8m8ujnzykjwmbeuj4ke9xk6ymng X-Rspam-User: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1794485706-286145 X-HE-Meta: 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 zhA8Wpif 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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 Tue, Nov 10, 2026 at 07:25:42PM +0800, Hao Ge wrote: > The PTE loop of the unmap path stops only at addr == end. With an > unaligned end addr never lands on end, so the loop walks past the > range and keeps clearing. With an unaligned start the loop begins > in the page containing start, which extends below the range. Either > way the unmap clears the mappings adjacent to the range, and that is > nearly impossible to debug afterwards. > > vmap only installs page-aligned, page-granular mappings, so an > unaligned unmap request is never a legitimate teardown, and there is > no way to tell which pages the caller meant. Check addr and end at > the entry of __vunmap_range_noflush() and bug out before any PTE is > cleared. > > 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 86fbb1d2b27a..0565cbfe325c 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -518,6 +518,8 @@ void __vunmap_range_noflush(unsigned long start, unsigned long end) > pgtbl_mod_mask mask = 0; > > BUG_ON(addr >= end); > + BUG_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end)); > + > pgd = pgd_offset_k(addr); > do { > next = pgd_addr_end(addr, end); > -- > 2.25.1 > I am not sure this is good to stop machine at all. WARN_ON_ONCE() and return? -- Uladzislau Rezki