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[79.242.54.84]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38f25915146sm4010991f8f.56.2025.02.14.00.11.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Feb 2025 00:11:56 -0800 (PST) Message-ID: Date: Fri, 14 Feb 2025 09:11:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] arm: pgtable: fix NULL pointer dereference issue To: Qi Zheng , linux@armlinux.org.uk, ezra@easyb.ch, hughd@google.com, ryan.roberts@arm.com, akpm@linux-foundation.org, muchun.song@linux.dev Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ezra Buehler , stable@vger.kernel.org References: <20250214030349.45524-1-zhengqi.arch@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: <20250214030349.45524-1-zhengqi.arch@bytedance.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: jZ-VnfK4KKbABpdsB8Tv8X_rB8cqVwiy-0JojZ1wxNY_1739520718 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 4596A180012 X-Rspamd-Server: rspam12 X-Stat-Signature: g5fzcqc1jmw5qtes1szozazkz1zh66x4 X-HE-Tag: 1739520721-814202 X-HE-Meta: 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 iFdJO167 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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: On 14.02.25 04:03, 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 > --- > Changes in v2: > - change Ezra's email address (Ezra Buehler) > - some cleanups (David Hildenbrand) > > arch/arm/mm/fault-armv.c | 38 ++++++++++++++++++++++++++------------ > 1 file changed, 26 insertions(+), 12 deletions(-) > > diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c > index 2bec87c3327d2..ea4c4e15f0d31 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 +122,18 @@ 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 pmd_start_addr, pmd_end_addr; Nit: reverse christmas tree would make us put this line at the very top. Maybe do the initialization directly: const unsigned long pmd_start_addr = ALIGN_DOWN(addr, PMD_SIZE); const unsigned long pmd_end_addr = pmd_start_addr + PMD_SIZE; > pgoff_t pgoff; > int aliases = 0; > > pgoff = vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT); > + pmd_start_addr = ALIGN_DOWN(addr, PMD_SIZE); > + pmd_end_addr = pmd_start_addr + PMD_SIZE; > > /* > * If we have any shared mappings that are in the same mm > @@ -141,6 +142,14 @@ make_coherent(struct address_space *mapping, struct vm_area_struct *vma, > */ > flush_dcache_mmap_lock(mapping); > vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) { > + /* > + * If we are using split PTE locks, then we need to take the pte > + * lock. Otherwise we are using shared mm->page_table_lock which > + * is already locked, thus cannot take it. > + */ > + bool need_lock = IS_ENABLED(CONFIG_SPLIT_PTE_PTLOCKS); > + unsigned long mpnt_addr; > + > /* > * If this VMA is not in our MM, we can ignore it. > * Note that we intentionally mask out the VMA > @@ -151,7 +160,12 @@ 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; > + > + /* Avoid deadlocks by not grabbing the same PTE lock again. */ > + if (mpnt_addr >= pmd_start_addr && mpnt_addr < pmd_end_addr) > + need_lock = false; > + aliases += adjust_pte(mpnt, mpnt_addr, pfn, need_lock); > } > flush_dcache_mmap_unlock(mapping); > if (aliases) > @@ -194,7 +208,7 @@ void update_mmu_cache_range(struct vm_fault *vmf, struct vm_area_struct *vma, > __flush_dcache_folio(mapping, folio); > if (mapping) { > if (cache_is_vivt()) > - make_coherent(mapping, vma, addr, ptep, pfn, vmf); > + make_coherent(mapping, vma, addr, ptep, pfn); > else if (vma->vm_flags & VM_EXEC) > __flush_icache_all(); > } Apart from that LGTM. Hoping it will work :) Acked-by: David Hildenbrand -- Cheers, David / dhildenb