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[2003:cb:c70c:a600:1e3e:c75:d269:867a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f2084ebdesm244867f8f.70.2025.02.12.00.30.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Feb 2025 00:30:21 -0800 (PST) Message-ID: <1399ea09-b53c-4eba-a023-34b8906c9bdd@redhat.com> Date: Wed, 12 Feb 2025 09:30:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm: pgtable: fix NULL pointer dereference issue To: Qi Zheng Cc: linux@armlinux.org.uk, ezra@easyb.ch, hughd@google.com, ryan.roberts@arm.com, akpm@linux-foundation.org, muchun.song@linux.dev, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20250212064002.55598-1-zhengqi.arch@bytedance.com> <54c30b02-c19e-4e51-8faf-7d6c5560ef6f@bytedance.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <54c30b02-c19e-4e51-8faf-7d6c5560ef6f@bytedance.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: bGPoRXsURIbFDFfgkzAoBBl-VIjaKNd-ShsRu-sJn6s_1739349023 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250212_003026_690695_4E1EFF6D X-CRM114-Status: GOOD ( 23.98 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 12.02.25 09:28, Qi Zheng wrote: > > > On 2025/2/12 16:20, David Hildenbrand wrote: >> On 12.02.25 07:40, Qi Zheng wrote: >>> When update_mmu_cache_range() is called by update_mmu_cache(), the vmf >>> parameter is NULL, which will cause a NULL pointer dereference issue in >>> adjust_pte(): >>> >>> Unable to handle kernel NULL pointer dereference at virtual address >>> 00000030 when read >>> Hardware name: Atmel AT91SAM9 >>> PC is at update_mmu_cache_range+0x1e0/0x278 >>> LR is at pte_offset_map_rw_nolock+0x18/0x2c >>> Call trace: >>>   update_mmu_cache_range from remove_migration_pte+0x29c/0x2ec >>>   remove_migration_pte from rmap_walk_file+0xcc/0x130 >>>   rmap_walk_file from remove_migration_ptes+0x90/0xa4 >>>   remove_migration_ptes from migrate_pages_batch+0x6d4/0x858 >>>   migrate_pages_batch from migrate_pages+0x188/0x488 >>>   migrate_pages from compact_zone+0x56c/0x954 >>>   compact_zone from compact_node+0x90/0xf0 >>>   compact_node from kcompactd+0x1d4/0x204 >>>   kcompactd from kthread+0x120/0x12c >>>   kthread from ret_from_fork+0x14/0x38 >>> Exception stack(0xc0d8bfb0 to 0xc0d8bff8) >>> >>> To fix it, do not rely on whether 'ptl' is equal to decide whether to >>> hold >>> the pte lock, but decide it by whether CONFIG_SPLIT_PTE_PTLOCKS is >>> enabled. In addition, if two vmas map to the same PTE page, there is no >>> need to hold the pte lock again, otherwise a deadlock will occur. Just >>> add >>> the need_lock parameter to let adjust_pte() know this information. >>> >>> Reported-by: Ezra Buehler >>> Closes: >>> https://lore.kernel.org/lkml/CAM1KZSmZ2T_riHvay+7cKEFxoPgeVpHkVFTzVVEQ1BO0cLkHEQ@mail.gmail.com/ >>> Fixes: fc9c45b71f43 ("arm: adjust_pte() use pte_offset_map_rw_nolock()") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Qi Zheng >>> --- >>>   arch/arm/mm/fault-armv.c | 40 ++++++++++++++++++++++++++++------------ >>>   1 file changed, 28 insertions(+), 12 deletions(-) >>> >>> diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c >>> index 2bec87c3327d2..3627bf0957c75 100644 >>> --- a/arch/arm/mm/fault-armv.c >>> +++ b/arch/arm/mm/fault-armv.c >>> @@ -62,7 +62,7 @@ static int do_adjust_pte(struct vm_area_struct *vma, >>> unsigned long address, >>>   } >>>   static int adjust_pte(struct vm_area_struct *vma, unsigned long >>> address, >>> -              unsigned long pfn, struct vm_fault *vmf) >>> +              unsigned long pfn, bool need_lock) >>>   { >>>       spinlock_t *ptl; >>>       pgd_t *pgd; >>> @@ -99,12 +99,11 @@ static int adjust_pte(struct vm_area_struct *vma, >>> unsigned long address, >>>       if (!pte) >>>           return 0; >>> -    /* >>> -     * If we are using split PTE locks, then we need to take the page >>> -     * lock here.  Otherwise we are using shared mm->page_table_lock >>> -     * which is already locked, thus cannot take it. >>> -     */ >>> -    if (ptl != vmf->ptl) { >>> +    if (need_lock) { >>> +        /* >>> +         * Use nested version here to indicate that we are already >>> +         * holding one similar spinlock. >>> +         */ >>>           spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); >>>           if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pmd)))) { >>>               pte_unmap_unlock(pte, ptl); >>> @@ -114,7 +113,7 @@ static int adjust_pte(struct vm_area_struct *vma, >>> unsigned long address, >>>       ret = do_adjust_pte(vma, address, pfn, pte); >>> -    if (ptl != vmf->ptl) >>> +    if (need_lock) >>>           spin_unlock(ptl); >>>       pte_unmap(pte); >>> @@ -123,16 +122,17 @@ static int adjust_pte(struct vm_area_struct >>> *vma, unsigned long address, >>>   static void >>>   make_coherent(struct address_space *mapping, struct vm_area_struct >>> *vma, >>> -          unsigned long addr, pte_t *ptep, unsigned long pfn, >>> -          struct vm_fault *vmf) >>> +          unsigned long addr, pte_t *ptep, unsigned long pfn) >>>   { >>>       struct mm_struct *mm = vma->vm_mm; >>>       struct vm_area_struct *mpnt; >>>       unsigned long offset; >>> +    unsigned long start; >>>       pgoff_t pgoff; >>>       int aliases = 0; >>>       pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT); >>> +    start = ALIGN_DOWN(addr, PMD_SIZE); >> >> I assume you can come up with a better name than "start" :) >> >> aligned_addr ... pmd_start_addr ... >> >> Maybe simply >> >> pmd_start_addr = ALIGN_DOWN(addr, PMD_SIZE); >> pmd_end_addr = addr + PMD_SIZE; > > you mean: > > pmd_end_addr = pmd_start_addr + PMD_SIZE; > > Right? Yes :) >> >>> + >>>           /* >>>            * If this VMA is not in our MM, we can ignore it. >>>            * Note that we intentionally mask out the VMA >>> @@ -151,7 +159,15 @@ make_coherent(struct address_space *mapping, >>> struct vm_area_struct *vma, >>>           if (!(mpnt->vm_flags & VM_MAYSHARE)) >>>               continue; >>>           offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; >>> -        aliases += adjust_pte(mpnt, mpnt->vm_start + offset, pfn, vmf); >>> +        mpnt_addr = mpnt->vm_start + offset; >>> +        /* >>> +         * If mpnt_addr and addr are mapped to the same PTE page, there >>> +         * is no need to hold the pte lock again, otherwise a deadlock >>> +         * will occur. >> >> /* >>  * Avoid deadlocks by not grabbing the PTE lock if we already hold the >>  * PTE lock of this PTE table in the caller. >>  */ > > Maybe just: > > /* Avoid deadlocks by not grabbing the same PTE lock again. */ > Agreed. -- Cheers, David / dhildenb