From nobody Sun Feb 8 00:49:30 2026 Received: from mail-pg1-f180.google.com (mail-pg1-f180.google.com [209.85.215.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B86C228C871 for ; Wed, 8 Oct 2025 05:28:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759901290; cv=none; b=JHN2JpYINhLvMcW2oDCfSJWTmG+dszMPX8yKoboxG9z+GQLN3+3hSbnjeeNfWL6WxOQquOTlFQU7KGlyqfA9trW7hx9eZQWDP/pVE4xv7bmmq2vCXvmZWBpreq1jIrvGXVfgQhlUzFHfcTKY4eToOUxSEQQIlzotq8lvkGD2xfs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759901290; c=relaxed/simple; bh=AC95x54JN1lRJt8eqwpof77duFRSx5Dj0tjKcKFDpSM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qcbingbZqDW9kBn2kUByqSFVFQhX1LCipW/mTDmzI6rQPYlXQ0+NhcsEvNP+tI8YPiTHJ3P4R/tOgDsSWZ7o/8/rgJMCqVSVq5bEPgfmhdkxCwtMelK3Cxcl8BZca/onLQmVaxqaH33PKBB5EbYTTsn7RjKyiFHsdqWAmwLOm9k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=bmGEIvPF; arc=none smtp.client-ip=209.85.215.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bmGEIvPF" Received: by mail-pg1-f180.google.com with SMTP id 41be03b00d2f7-b551350adfaso6257277a12.3 for ; Tue, 07 Oct 2025 22:28:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1759901288; x=1760506088; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=BMqvRrCCbf00Rf1hkLneqb6IWYGGdZT3hFbhVoMk1mQ=; b=bmGEIvPFRttG1TKlyDQhafPE4RZiPgGaQR8yjVBWPsrcWqCFzIPlFRG5c+FliHKsUS QujdgvaRVHxnJ0goWQKAX0AHa1n8hg24D8Fg1sAN4AItLD/8frX96hVh2Oe4UAIr2qYh 6nLBfYO5lEQB7rNmdnsLMXDXvzeKIlahtcUzEE/2djvZUImBtSCeXAPr6soLyzUYBs7J QSjun2gtFN4rZL0JlQUkQhsYkdJbBUsuSrLWKHPVvsDKYVdvilrc0hV/BF5rC0O/khqU WYV+fVFq0KLTbKDlqHbk3gLGzcy5CTJBJeUdqSKjk2AaWT2u2WJyeMqSvp6xMjmqr14N 7Y9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759901288; x=1760506088; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=BMqvRrCCbf00Rf1hkLneqb6IWYGGdZT3hFbhVoMk1mQ=; b=JcJSwqQ0ZFH6dcRVgOfadYQ2YtDseVC6RzcZY2GOJPdeyMVjHjeueudasXiXD89JDC WF41AwBuPMtvYlDlYDLi4b0DZY8o5t5KrQRVACHedrXAfKLazoJmlCtPQ/VFnf26mLwc MUdshYj8Kkh6npme7rUJkVjkwh/g53vNkQbJVVT66LUvHTuTRASaF5lKWU7cMqnE0ZWC L5ijPu5u7HxKINGIQefSfrInfhvQ4p1axButUS2fqg+OAVPAM3Q7KCtCudGzLVstE9K0 pj8nFFyH4bFfigY7ilfbGSFm7cSTFx1iWQS/qHa0uttS8980scFk7trfwLA3ikmdT6Cw Lf2Q== X-Forwarded-Encrypted: i=1; AJvYcCWIW2ANU+buu+jTW8ajDtGqokBFW9eatKUUOw8o+4MdoagQxPI5KIAT+ee+5FWSpu5VQdyerIUYYSbbbOo=@vger.kernel.org X-Gm-Message-State: AOJu0YzW3yyufUjnAjRNsAuTNKdCb1AgzMratAT5AdQjFjl5RyK/JAa0 w5a2RziFbLbcHde5ykzOEpI38RjUr17SIXxRN51XxzaluoKQA7h3oK9g X-Gm-Gg: ASbGncsjxPfxIyIKi9bsOvraNmO/2PCLaWeStZeZxmdfuDLq8kWXM9JsCqpWlRDD6fs bUHEO24uLFRCTubt6NU/IXMBLVcq8uI0tBoqTpjPduOL+MXqkkOlH9d82e6YH4sR6FXWvmc3MQs 1SLUqYMqxPeOW5YrBmtVpGBnSr0anyzWg4a+ft1uq57MMCVIaMUUvcvIpfP0CIARcFTAYHEoCKv +gmXyi3362rv6d02poNV5nPDSca2fw6Vv2D0IRP4js+kzXVbuEi7DTRRdE8Dc1vNTNJCH3RlwUb +EEZa3t3D4AxPvf3hBq/+j4xjpsgzAcAYyj29AJp8WzvtkJINtyDNRyUz5ZzQ1p4zboRsJmeD1y WM1s9FNlO6ECig6jWHx9tHzj0wZdrgAurnLYLRc3O8M1pBeSFnz1vL12xNDW/drItfO4a57Izyu 1juz/5Tqxk8fSYvGlTGGPhrEI= X-Google-Smtp-Source: AGHT+IFbymgP7acspeJIYGYr+yCoZt35ZnCOv65FC9GFvmEZGXKh8iwKgmM+q7JvQSYy5hZmRSAA/Q== X-Received: by 2002:a17:903:3c4d:b0:267:44e6:11d3 with SMTP id d9443c01a7336-29027379986mr28771885ad.21.1759901287971; Tue, 07 Oct 2025 22:28:07 -0700 (PDT) Received: from deepanshu-kernel-hacker.. ([2405:201:682f:389d:4c4:4e8:dff0:bf0]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-28e8d1f1a75sm184147135ad.125.2025.10.07.22.28.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Oct 2025 22:28:07 -0700 (PDT) From: Deepanshu Kartikey To: muchun.song@linux.dev, osalvador@suse.de, david@redhat.com, akpm@linux-foundation.org, broonie@kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com Subject: [PATCH v4] hugetlbfs: check for shareable lock before calling huge_pmd_unshare() Date: Wed, 8 Oct 2025 10:57:59 +0530 Message-ID: <20251008052759.469714-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251003174553.3078839-1-kartikey406@gmail.com> References: <20251003174553.3078839-1-kartikey406@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Brow= n. 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 huget= lb_vmdelete_list") Suggested-by: Oscar Salvador Suggested-by: David Hildenbrand Link: https://lore.kernel.org/mm-commits/20250925203504.7BE02C4CEF7@smtp.ke= rnel.org/ [v1] Link: https://lore.kernel.org/mm-commits/20250928185232.BEDB6C4CEF0@smtp.ke= rnel.org/ [v2] Link: https://lore.kernel.org/linux-mm/20251003174553.3078839-1-kartikey406= @gmail.com/ [v3] Signed-off-by: Deepanshu Kartikey Acked-by: Oscar Salvador --- 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, pgo= ff_t start, pgoff_t end, if (!hugetlb_vma_trylock_write(vma)) continue; =20 - /* - * 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 =3D vma_offset_start(vma, start); v_end =3D vma_offset_end(vma, end); =20 @@ -496,7 +488,7 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgof= f_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, s= truct vm_area_struct *vma, } =20 ptl =3D 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 =3D true; --=20 2.43.0