From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794333991; b=GXHEEJbNIQfgfpe3D8TfVuqicN9BEAatO+DRE7wOifJoUJCup/SBZYI10kY9kK5KSfI6 FwueyceFTCuQcsy7RXYNQMJwMt3EF8tDRMqZY5oLtEDjYTf4Gwx1z8wvH3mUaR3GBUg2A vZz6PFwB/pq1nbWlpBq47Zcu7b8Z0aHZ+UIKU5ihk3+T3hHJSGzKwBqAlojjPQFslyLKb QsiMVqHE43w8gphJUSZMCv3lcQ9xOHVILa8kyAOLuQiAH0ZORfccvT54Sibryym+yewUL QYPE63aM7eksnxNFvmZ9jNoTR+VHRUmYctJQAfDBfxuX7Ml5E0vur9TCIFHl3E4rzTQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794333991; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=12PTd/6Pp2GXmH1FksLbbJ56lhHXgLf+F7jZdkRnKy0=; b=vvLVPBZLoYOCb8IafaiablvdccRCR7u11D3buNbh0/MbwSDvXuaNKuCjmNx18+lBqM9q fL46UfYBy+mH47+fboIC17shCwIod4xZlUfQX4TOAjnIrLelANaSDclzjCB3gBctLoyz7 wGI/zovWTRdCPbZhBuvm1TGMbhjhsj/lDpDRGUBu9vac6n2ETDFHfLJ5RzNCQOpn+dX+8 aUXgdYwy+kJR0qnvEwXzp3fuH0UYbsJHgWtByyjBGrW6aMR7F3OuCG3sVLpJECEgOC7yl d3kaZKER7oiuti7SUNIUwZfeIJuovQiHJTBdW76IxaQanL91N58LB8mqyjovKt9vtVg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nngIBkap; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7C15A60A261F for ; Tue, 10 Nov 2026 18:06:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=nngIBkap Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9884A1F008A3; Tue, 10 Nov 2026 18:06:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794333991; bh=12PTd/6Pp2GXmH1FksLbbJ56lhHXgLf+F7jZdkRnKy0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nngIBkapmiGk1P+BuKFDmh853ZISBiHoutLarImRn6bbtlvEYY7bAJU+3+SK7EIYe cy0dHgWRMS6oAXDaK98dG7MprZF2LEZQ46PxOH70NE6XMYOwAnePBO99FIYKIiNK/A xT9j29e/txFRppiyW5+VKuAw8EgEMm+sZWh89bj8+FkxEUfz396nVGBGwdJI6JByBs Wi6ikhWmN6/WKcirdgLBl84xT7DNOS0sbd5ay+AUOD3fTPcOSThCgalUVfcE9os+8g 1VkJE3eHYFCpx2xf83ij0RktxZYFLE/ccQulZ3m/SQ1R01KcpbcClYq1Kn2i78wtAJ 4jwFCKE37D7cg== From: Sasha Levin To: stable@vger.kernel.org Cc: Daeho Jeong , stable@kernel.org, Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.1.y] f2fs: disallow mmap write and data-modifying fallocate on atomic files Date: Tue, 10 Nov 2026 13:06:28 -0500 Message-ID: <20261110180356.3017239-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107054834-failed-6.1-06dfe4a7eb69@kernel.org> References: <20261107054834-failed-6.1-06dfe4a7eb69@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Daeho Jeong [ Upstream commit 06dfe4a7eb696d868b196c2a49873142f19bd862 ] Stores through a shared writable mapping and fallocate with FALLOC_FL_PUNCH_HOLE, FALLOC_FL_ZERO_RANGE, FALLOC_FL_COLLAPSE_RANGE or FALLOC_FL_INSERT_RANGE do not go through ->write_begin, so they bypass the COW inode and modify the original inode directly. Reject them while the file is in atomic write mode, as fallocate already does for pinned and compressed files. A write fault gets SIGBUS and fallocate gets -EOPNOTSUPP. fallocate without these flags only preallocates blocks and stays allowed. f2fs_vm_page_mkwrite() cannot take inode_lock, so check the flag under invalidate_lock, and hold invalidate_lock in f2fs_ioc_start_atomic_write() from the flush until the flag is set. Otherwise a fault could check the flag, then start_atomic_write could flush and set the flag, and the fault would dirty the folio afterwards. Cc: stable@kernel.org Fixes: 3db1de0e582c ("f2fs: change the current atomic write way") Signed-off-by: Daeho Jeong Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim [ sashal: replaced the shared out_unlock cleanup with explicit invalidate_lock releases on all error exits ] Signed-off-by: Sasha Levin --- fs/f2fs/file.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index bde1c9cfe1df4..13a61e6ef448f 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -102,6 +102,18 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf) file_update_time(vmf->vma->vm_file); filemap_invalidate_lock_shared(inode->i_mapping); + + /* + * mmap stores bypass the COW inode and would break atomicity. Check + * under invalidate_lock: f2fs_ioc_start_atomic_write() holds it while + * flushing dirty pages and setting FI_ATOMIC_FILE, so either it sees + * our dirty page and writes it back, or we see the flag. + */ + if (unlikely(f2fs_is_atomic_file(inode))) { + err = -EOPNOTSUPP; + goto out_sem; + } + lock_page(page); if (unlikely(page->mapping != inode->i_mapping || page_offset(page) > i_size_read(inode) || @@ -1888,9 +1900,11 @@ static long f2fs_fallocate(struct file *file, int mode, /* * Pinned file should not support partial truncation since the block - * can be used by applications. + * can be used by applications. Atomic files should not either, since + * these modify the original inode directly and break atomicity. */ - if ((f2fs_compressed_file(inode) || f2fs_is_pinned_file(inode)) && + if ((f2fs_compressed_file(inode) || f2fs_is_pinned_file(inode) || + f2fs_is_atomic_file(inode)) && (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE | FALLOC_FL_INSERT_RANGE))) { ret = -EOPNOTSUPP; @@ -2174,6 +2188,8 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) goto out; f2fs_down_write(&fi->i_gc_rwsem[WRITE]); + /* serialize with f2fs_vm_page_mkwrite(), see the comment there */ + filemap_invalidate_lock(inode->i_mapping); /* * Should wait end_io to count F2FS_WB_CP_DATA correctly by @@ -2184,6 +2200,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) inode->i_ino, get_dirty_pages(inode)); ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX); if (ret) { + filemap_invalidate_unlock(inode->i_mapping); f2fs_up_write(&fi->i_gc_rwsem[WRITE]); goto out; } @@ -2193,6 +2210,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) /* Create a COW inode for atomic write */ pinode = f2fs_iget(inode->i_sb, fi->i_pino); if (IS_ERR(pinode)) { + filemap_invalidate_unlock(inode->i_mapping); f2fs_up_write(&fi->i_gc_rwsem[WRITE]); ret = PTR_ERR(pinode); goto out; @@ -2201,6 +2219,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) ret = f2fs_get_tmpfile(mnt_userns, pinode, &fi->cow_inode); iput(pinode); if (ret) { + filemap_invalidate_unlock(inode->i_mapping); f2fs_up_write(&fi->i_gc_rwsem[WRITE]); goto out; } @@ -2215,6 +2234,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) ret = f2fs_do_truncate_blocks(fi->cow_inode, 0, true); if (ret) { + filemap_invalidate_unlock(inode->i_mapping); f2fs_up_write(&fi->i_gc_rwsem[WRITE]); goto out; } @@ -2229,6 +2249,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp) stat_inc_atomic_inode(inode); set_inode_flag(inode, FI_ATOMIC_FILE); + filemap_invalidate_unlock(inode->i_mapping); f2fs_up_write(&fi->i_gc_rwsem[WRITE]); f2fs_update_time(sbi, REQ_TIME); -- 2.53.0