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[2003:cb:c748:ba00:1c00:48ea:7b5a:c12b]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-35ef5d2e73dsm13920655f8f.16.2024.06.11.05.32.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Jun 2024 05:32:25 -0700 (PDT) Message-ID: Date: Tue, 11 Jun 2024 14:32:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: fix possible OOB in numa_rebuild_large_mapping() To: Kefeng Wang , Andrew Morton Cc: ying.huang@intel.com, Baolin Wang , linux-mm@kvack.org, John Hubbard , Mel Gorman , Ryan Roberts , liushixin2@huawei.com References: <20240607103241.1298388-1-wangkefeng.wang@huawei.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK 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X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Stat-Signature: 7zf81555p1rp8j5s4o7gmjqfg1crw4yr X-Rspamd-Queue-Id: BDB4714001C X-Rspam-User: X-HE-Tag: 1718109150-327382 X-HE-Meta: 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mremap(), the virtual address only > require PAGE_SIZE aligned, also pte is moved to new in move_page_tables(), > then traverse the new pte in numa_rebuild_large_mapping() will hint the > following issue, > > Unable to handle kernel paging request at virtual address 00000a80c021a788 > Mem abort info: > ESR = 0x0000000096000004 > EC = 0x25: DABT (current EL), IL = 32 bits > SET = 0, FnV = 0 > EA = 0, S1PTW = 0 > FSC = 0x04: level 0 translation fault > Data abort info: > ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 > CM = 0, WnR = 0, TnD = 0, TagAccess = 0 > GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > user pgtable: 4k pages, 48-bit VAs, pgdp=00002040341a6000 > [00000a80c021a788] pgd=0000000000000000, p4d=0000000000000000 > Internal error: Oops: 0000000096000004 [#1] SMP > ... > CPU: 76 PID: 15187 Comm: git Kdump: loaded Tainted: G W 6.10.0-rc2+ #209 > Hardware name: Huawei TaiShan 2280 V2/BC82AMDD, BIOS 1.79 08/21/2021 > pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : numa_rebuild_large_mapping+0x338/0x638 > lr : numa_rebuild_large_mapping+0x320/0x638 > sp : ffff8000b41c3b00 > x29: ffff8000b41c3b30 x28: ffff8000812a0000 x27: 00000000000a8000 > x26: 00000000000000a8 x25: 0010000000000001 x24: ffff20401c7170f0 > x23: 0000ffff33a1e000 x22: 0000ffff33a76000 x21: ffff20400869eca0 > x20: 0000ffff33976000 x19: 00000000000000a8 x18: ffffffffffffffff > x17: 0000000000000000 x16: 0000000000000020 x15: ffff8000b41c36a8 > x14: 0000000000000000 x13: 205d373831353154 x12: 5b5d333331363732 > x11: 000000000011ff78 x10: 000000000011ff10 x9 : ffff800080273f30 > x8 : 000000320400869e x7 : c0000000ffffd87f x6 : 00000000001e6ba8 > x5 : ffff206f3fb5af88 x4 : 0000000000000000 x3 : 0000000000000000 > x2 : 0000000000000000 x1 : fffffdffc0000000 x0 : 00000a80c021a780 > Call trace: > numa_rebuild_large_mapping+0x338/0x638 > do_numa_page+0x3e4/0x4e0 > handle_pte_fault+0x1bc/0x238 > __handle_mm_fault+0x20c/0x400 > handle_mm_fault+0xa8/0x288 > do_page_fault+0x124/0x498 > do_translation_fault+0x54/0x80 > do_mem_abort+0x4c/0xa8 > el0_da+0x40/0x110 > el0t_64_sync_handler+0xe4/0x158 > el0t_64_sync+0x188/0x190 > > Fix it by correct the start and end, which may lead to only rebuild part > of large mapping in one numa page fault, there is no issue since other part > could rebuild by another pagefault. > > Fixes: d2136d749d76 ("mm: support multi-size THP numa balancing") > Signed-off-by: Kefeng Wang > --- > mm/memory.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index db9130488231..0ad57b6485ca 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5223,15 +5223,21 @@ static void numa_rebuild_single_mapping(struct vm_fault *vmf, struct vm_area_str > update_mmu_cache_range(vmf, vma, fault_addr, fault_pte, 1); > } > > -static void numa_rebuild_large_mapping(struct vm_fault *vmf, struct vm_area_struct *vma, > - struct folio *folio, pte_t fault_pte, > - bool ignore_writable, bool pte_write_upgrade) > +static void numa_rebuild_large_mapping(struct vm_fault *vmf, > + struct vm_area_struct *vma, struct folio *folio, int nr_pages, > + pte_t fault_pte, bool ignore_writable, bool pte_write_upgrade) > { > int nr = pte_pfn(fault_pte) - folio_pfn(folio); > - unsigned long start = max(vmf->address - nr * PAGE_SIZE, vma->vm_start); > - unsigned long end = min(vmf->address + (folio_nr_pages(folio) - nr) * PAGE_SIZE, vma->vm_end); > - pte_t *start_ptep = vmf->pte - (vmf->address - start) / PAGE_SIZE; > - unsigned long addr; > + unsigned long folio_size = nr_pages * PAGE_SIZE; Just re-read folio_nr_pages() here, it's cheap. Or even better, use folio_size(); > + unsigned long addr = vmf->address; > + unsigned long start, end, align_addr; > + pte_t *start_ptep; > + > + align_addr = ALIGN_DOWN(addr, folio_size); > + start = max3(addr - nr * PAGE_SIZE, align_addr, vma->vm_start); > + end = min3(addr + (nr_pages - nr) * PAGE_SIZE, align_addr + folio_size, Please avoid mixing nr_pages and folio_size. > + vma->vm_end); > + start_ptep = vmf->pte - (addr - start) / PAGE_SIZE; writable); I am not able to convince myself that the old code could not have resulted in a vmf->pte that underflows the page table. Am I correct? Now align_addr would make sure that we are always within one page table (as long as our folio size does not exceed PMD size :) ). Can we use PMD_SIZE instead for that, something like the following? /* Stay within the VMA and within the page table. */ pt_start = ALIGN_DOWN(addr, PMD_SIZE); start = max3(addr - nr << PAGE_SHIFT, pt_start, vma->vm_start); end = min3(addr + folio_size - nr << PAGE_SHIFT, pt_start + PMD_SIZE, vma->vm_end); start_ptep = vmf->pte - (addr - start) >> PAGE_SHIFT; -- Cheers, David / dhildenb