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Thu, 09 Oct 2025 14:04:08 +0800 From: To: "'Andrew Morton'" Cc: , , , References: <20251009035943.526-1-yadong.qi@linux.alibaba.com> <20251008211714.5a8b9fbb57dbe454cd4a9c6d@linux-foundation.org> In-Reply-To: <20251008211714.5a8b9fbb57dbe454cd4a9c6d@linux-foundation.org> Subject: RE: [PATCH] mm: vmalloc: BUG_ON if mapping size is not PAGE_SIZE aligned Date: Thu, 9 Oct 2025 14:04:08 +0800 Message-ID: <000d01dc38e2$86ab7460$94025d20$@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: quoted-printable X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQEfqa1TUb5DdaMeKJ5HQMODeYaJIQI0Cl/AtiDDkRA= Content-Language: zh-cn X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 308641C000A X-Stat-Signature: nymcgqnjgynqn3f79se1mb84ch4o8i4b X-Rspam-User: X-HE-Tag: 1759989854-23965 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > -----Original Message----- > From: Andrew Morton > Sent: 2025=C4=EA10=D4=C29=C8=D5 12:17 > To: Yadong Qi > Cc: urezki@gmail.com; linux-mm@kvack.org; = linux-kernel@vger.kernel.org; > ying.huang@linux.alibaba.com > Subject: Re: [PATCH] mm: vmalloc: BUG_ON if mapping size is not = PAGE_SIZE > aligned >=20 > On Thu, 9 Oct 2025 11:59:43 +0800 Yadong Qi = > wrote: >=20 > > In mm/vmalloc.c, the function vmap_pte_range() assumes that the > > mapping size is aligned to PAGE_SIZE. If this assumption is > > violated, the loop will become infinite because the termination > > condition (`addr !=3D end`) will never be met. This can lead to > > overwriting other VA ranges and/or random pages physically follow > > the page table. > > > > It's the caller's responsibility to ensure that the mapping size > > is aligned to PAGE_SIZE. However, the memory corruption is hard > > to root cause. To identify the programming error in the caller > > easier, check whether the mapping size is PAGE_SIZE aligned with > > BUG_ON(). > > > > .. > > > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -100,6 +100,8 @@ static int vmap_pte_range(pmd_t *pmd, unsigned = long > addr, unsigned long end, > > struct page *page; > > unsigned long size =3D PAGE_SIZE; > > > > + BUG_ON(!PAGE_ALIGNED(end - addr)); > > + > > pfn =3D phys_addr >> PAGE_SHIFT; > > pte =3D pte_alloc_kernel_track(pmd, addr, mask); > > if (!pte) >=20 > We try to avoid adding BUG()s - deliberately crashing the kernel is > pretty cruel to the user. It's far better to WARN and to continue in > some fashion so the user can at least gather logs, etc. >=20 > How about >=20 > if (WARN_ON(!PAGE_ALIGNED(end - addr))) > return -ENOMEM; >=20 > ? >=20 > (Or VM_WARN_ON) Sure, I will send a new patch with WARN_ON. Best Regard Yadong