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[80.187.83.189]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fb489accbsm196059665e9.14.2025.10.13.01.27.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Oct 2025 01:27:30 -0700 (PDT) Message-ID: Date: Mon, 13 Oct 2025 10:27:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] hugetlbfs: check for shareable lock before calling huge_pmd_unshare() To: Deepanshu Kartikey , muchun.song@linux.dev, osalvador@suse.de, akpm@linux-foundation.org, broonie@kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com References: <20251003174553.3078839-1-kartikey406@gmail.com> <20251008052759.469714-1-kartikey406@gmail.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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20251008052759.469714-1-kartikey406@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -Rl7QAisrGJ9vMEWzNt1mksoeMAHzeLGSL__ZAyNfhk_1760344052 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 56tbnrjgn7jt9g6fx58h3zijem6ne7g3 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 30551180007 X-HE-Tag: 1760344055-68201 X-HE-Meta: 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 DPtXcU7e 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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 08.10.25 07:27, Deepanshu Kartikey wrote: > When hugetlb_vmdelete_list() processes VMAs during truncate operations, > it may encounter VMAs where huge_pmd_unshare() is called without the > required shareable lock. This triggers an assertion failure in > hugetlb_vma_assert_locked(). > > The previous fix in commit dd83609b8898 ("hugetlbfs: skip VMAs without > shareable locks in hugetlb_vmdelete_list") skipped entire VMAs without > shareable locks to avoid the assertion. However, this prevented pages > from being unmapped and freed, causing a regression in fallocate(PUNCH_HOLE) > operations where pages were not freed immediately, as reported by Mark Brown. > > Instead of skipping VMAs or adding new flags, check __vma_shareable_lock() > directly in __unmap_hugepage_range() right before calling huge_pmd_unshare(). > This ensures PMD unsharing only happens when the VMA has a shareable lock > structure, while still allowing page unmapping and freeing to proceed for > all VMAs. > > Reported-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com > Tested-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com > Reported-by: Mark Brown > Fixes: dd83609b8898 ("hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list") > Suggested-by: Oscar Salvador > Suggested-by: David Hildenbrand > Link: https://lore.kernel.org/mm-commits/20250925203504.7BE02C4CEF7@smtp.kernel.org/ [v1] > Link: https://lore.kernel.org/mm-commits/20250928185232.BEDB6C4CEF0@smtp.kernel.org/ [v2] > Link: https://lore.kernel.org/linux-mm/20251003174553.3078839-1-kartikey406@gmail.com/ [v3] > Signed-off-by: Deepanshu Kartikey > --- > Changes in v4: > - Simplified approach per Oscar's suggestion: check __vma_shareable_lock() > directly in __unmap_hugepage_range() before calling huge_pmd_unshare() > - Removed ZAP_FLAG_NO_UNSHARE flag per David's feedback to avoid polluting > generic mm.h header > - Reverted hugetlb_vmdelete_list() to not skip VMAs > > Changes in v3: > - Added ZAP_FLAG_NO_UNSHARE to skip only PMD unsharing, not entire VMA > > Changes in v2: > - Skip entire VMAs without shareable locks in hugetlb_vmdelete_list() > (caused PUNCH_HOLE regression) > > Changes in v1: > - Initial fix attempt > --- > fs/hugetlbfs/inode.c | 10 +--------- > mm/hugetlb.c | 2 +- > 2 files changed, 2 insertions(+), 10 deletions(-) > > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c > index 9c94ed8c3ab0..1e040db18b20 100644 > --- a/fs/hugetlbfs/inode.c > +++ b/fs/hugetlbfs/inode.c > @@ -478,14 +478,6 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end, > if (!hugetlb_vma_trylock_write(vma)) > continue; > > - /* > - * Skip VMAs without shareable locks. Per the design in commit > - * 40549ba8f8e0, these will be handled by remove_inode_hugepages() > - * called after this function with proper locking. > - */ > - if (!__vma_shareable_lock(vma)) > - goto skip; > - > v_start = vma_offset_start(vma, start); > v_end = vma_offset_end(vma, end); > > @@ -496,7 +488,7 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end, > * vmas. Therefore, lock is not held when calling > * unmap_hugepage_range for private vmas. > */ > -skip: > + > hugetlb_vma_unlock_write(vma); > } > } > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 6cac826cb61f..9ed85ab8420e 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -5885,7 +5885,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, > } > > ptl = huge_pte_lock(h, mm, ptep); > - if (huge_pmd_unshare(mm, vma, address, ptep)) { > + if (__vma_shareable_lock(vma) && huge_pmd_unshare(mm, vma, address, ptep)) { > spin_unlock(ptl); > tlb_flush_pmd_range(tlb, address & PUD_MASK, PUD_SIZE); > force_flush = true; Wondering, couldn't we handle that in huge_pmd_unshare()? diff --git a/mm/hugetlb.c b/mm/hugetlb.c index eed59cfb5d218..f167cec4a5acc 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -7598,13 +7598,14 @@ int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, p4d_t *p4d = p4d_offset(pgd, addr); pud_t *pud = pud_offset(p4d, addr); - i_mmap_assert_write_locked(vma->vm_file->f_mapping); - hugetlb_vma_assert_locked(vma); if (sz != PMD_SIZE) return 0; if (!ptdesc_pmd_pts_count(virt_to_ptdesc(ptep))) return 0; + i_mmap_assert_write_locked(vma->vm_file->f_mapping); + hugetlb_vma_assert_locked(vma); + pud_clear(pud); /* * Once our caller drops the rmap lock, some other process might be -- Cheers David / dhildenb