From nobody Fri Dec 19 17:18:45 2025 Received: from mail-io1-f71.google.com (mail-io1-f71.google.com [209.85.166.71]) (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 3E5AA19F43A for ; Tue, 14 Oct 2025 03:35:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.71 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760412943; cv=none; b=lLs8JxbOW8SIPZ17AvUHsHags3cDHDhOpgNod7etmIqpfqxeDolRQm0pnRVb8OmMFOjrOwy6aONkr/LLJyUcM4glcPcMBhFkVByJxDCQP6V0eRHaZIW+4O3r1rLPAfPgMhPRGH/les7et5Y0q9+yCQtHL9XXD9nqQHw2NSo14k8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760412943; c=relaxed/simple; bh=6HQf9ge5tV/YSPkVdWYdYNiOVQcmwpNSNT01kJ3kr2Q=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=NOQtYBm1GPdSwBkm/MvcFr1TcmD+JccFHDfcUbMjgCtgOcOK6MUVKJjSmky4XIYM44H3VSPneCTb4gA1vL8KVsNrztu/5ad2MuRfaPohnAo8IN50F3PvuvacZD+o5lod1neAZT24vTnCR88Q/OcuqlO+dDo2zL4OWEqEKbVn714= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.166.71 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-io1-f71.google.com with SMTP id ca18e2360f4ac-93bbaa774e2so1181043939f.3 for ; Mon, 13 Oct 2025 20:35:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760412941; x=1761017741; h=to:from:subject:message-id:in-reply-to:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=P7zsBbEOiPceBFWAfYaITeXxB7rQF3O1VUKlbD74mTE=; b=B/K89RPlsFDuZm+QAgXOd0Xt2ds20CT9V9P9iumaYfcg0dpLlLnSB4oZ/ZXV7i/4eF qsQICUHs0aBvjr9iT6qW957szic6wn7sIDvhJjO08vp8atl29WF9+VDpbKmD3SSmU8cG /+VTbMpaNWBBJBEkFXDcYkZZQ/qC0HdmtzFiXyjGGh6Bvg7TrXYYPxYPnDUhIXP6o/h6 LNT9at3eHw6J4rgkKq6sIUkYvGfItr7uI6+xQEP6jVSzWIYyenL8+SAVXEVk+FcAYCoL XfgdvU5cNHTKTMsdKBk5GuqGB4pissyCKXSD1AaZ/+TCv3Kms/ooWgz+EGp/+NPXhyPc kl5g== X-Gm-Message-State: AOJu0YyMgewKZ0y+/lD8U+t1rl94OLoONK7PQhdYYU3iQ4MRaJguQjbh ON3wcOSFOXYQvw4HWSCB8JrGtQuDasg35yTROhKPagfIGWF4l/qxklwpdVHYM0nIh3ZkB8Oc+ky Wqqh4peWcBAftQmy+hG9PDFoAu809tbJd2YB1aRG5cDYUY2xlZxE9qbmH3ms= X-Google-Smtp-Source: AGHT+IHq09EtMES2y01sYYcmF/CEW07SjSwai7btqwUlokkvGf4KukX5QBPFokEZ8htNuGEQA1475rnM+vIocR5sw/Xw77xy+3Ck Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6e02:1c21:b0:42f:8e66:e8c5 with SMTP id e9e14a558f8ab-42f8e66e945mr235926755ab.4.1760412941344; Mon, 13 Oct 2025 20:35:41 -0700 (PDT) Date: Mon, 13 Oct 2025 20:35:41 -0700 In-Reply-To: <68d26261.a70a0220.4f78.0003.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68edc50d.050a0220.91a22.01f7.GAE@google.com> Subject: Forwarded: [PATCH v5] hugetlbfs: move lock assertions after early returns in huge_pmd_unshare() From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH v5] hugetlbfs: move lock assertions after early returns in = huge_pmd_unshare() Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.gi= t master 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 checking locks in the caller or skipping VMAs, move the lock assertions in huge_pmd_unshare() to after the early return checks. The assertions are only needed when actual PMD unsharing work will be performed. If the function returns early because sz !=3D PMD_SIZE or the PMD is not shared, no locks are required and assertions should not fire. This is cleaner than previous approaches because it keeps all the logic within huge_pmd_unshare() itself, while still allowing page unmapping and freeing to proceed for all VMAs. Reported-by: syzbot+f26d7c75c26ec19790e7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Df26d7c75c26ec19790e7 Fixes: dd83609b8898 ("hugetlbfs: skip VMAs without shareable locks in huget= lb_vmdelete_list") 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] Link: https://lore.kernel.org/linux-mm/20251008052759.469714-1-kartikey406@= gmail.com/ [v4] Signed-off-by: Deepanshu Kartikey --- Changes in v5: - Move lock assertions after early return checks in huge_pmd_unshare() per David's suggestion - cleaner approach that keeps logic within the function itself - Revert all previous approaches (VMA skipping, flag additions, caller chec= ks) Changes in v4: - Check __vma_shareable_lock() in __unmap_hugepage_range() before calling huge_pmd_unshare() per Oscar's suggestion - Remove ZAP_FLAG_NO_UNSHARE flag per David's feedback Changes in v3: - Add ZAP_FLAG_NO_UNSHARE to skip only PMD unsharing, not entire VMA Changes in v2: - Skip entire VMAs without shareable locks (caused PUNCH_HOLE regression) Changes in v1: - Initial fix attempt --- fs/hugetlbfs/inode.c | 10 +--------- mm/hugetlb.c | 5 ++--- 2 files changed, 3 insertions(+), 12 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 795ee393eac0..0455119716ec 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -7614,13 +7614,12 @@ int huge_pmd_unshare(struct mm_struct *mm, struct v= m_area_struct *vma, p4d_t *p4d =3D p4d_offset(pgd, addr); pud_t *pud =3D pud_offset(p4d, addr); =20 - i_mmap_assert_write_locked(vma->vm_file->f_mapping); - hugetlb_vma_assert_locked(vma); if (sz !=3D PMD_SIZE) return 0; if (!ptdesc_pmd_is_shared(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 --=20 2.34.1