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=1794332554; b=CuS2gr6jIb7Bg8JlhbidFD3SdbpUZp+3CBY6NxuWdM36YSAR7aY9oaWmi2XCse6iAQBg don1xXp6yYwG/0bPx47RS5Dys1v2vzwM/5IMtHdVbFHAX6FkSV6ec0JLwwiYN9dJsKWhV AlEN2kePh602qg2G96CmNu5wn7TuckTGTjEneRWASLI5g16PaPrB2uzdhf1vRTGDwczjH SWLYZ7CfmCR/7+zQOYk4DUCtZQwhDP+GzMi/xJvh0WQO3BMVSlYU3lLwiU12WICsxxemi IYlIoLC8cNOSxBoVORGa5NUuQKOIdKTnoR4zuQVL/ZUnfxnMenZLYtkXUexsopdHRzg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794332554; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=GqkUFWepws1vBwqcMm8H0kfanqhuDXTJwi7mc4C7ETY=; b=ievixSvRN3UyNxxx6FVDGLYew7yWIHh1R55mLy1m0hMJ4py+ZpahkFcGEdAjlj2GVOK1 mrOkP7zIFm4mMrMW5d8eI7xMIDCQ+WIilQHcwxtJFtFYCjXrpIc+kKeaqYEGJqUTSquQk nfe3rwIPS+S8ZCfIl1hUQ4YTS5ccpRP820HDqbHDeP2/5UQjiJNEb9VvNue+9rGCyuSOd Ds5TgUWUWP4HTd3MjysJl7JYuuiVriPDD67xuUj+82yJxVZE+a6HBdUlW22p+mpsfrb6d klxPB5Z1lZqnWhDujNO3tGgkg4TyEYaxSson1B0LTotct9PXN3C7tKIEQu99iBA15eg== 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=BsykCArz; 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 4918760A3803 for ; Tue, 10 Nov 2026 17:42:34 +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=BsykCArz Received: by smtp.kernel.org (Postfix) with ESMTPSA id 233F41F008A3; Tue, 10 Nov 2026 17:42:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794332553; bh=GqkUFWepws1vBwqcMm8H0kfanqhuDXTJwi7mc4C7ETY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=BsykCArz0Af03EnoFuLAlyDvCm7JevH0vYHNVLGZKBt2ff96vLgJkSNizn2Qmztzq pB3jsH5uf6ivfZDv1a5sItq79UNbBXtCKWBSY1PLE/IzOYXrjDf56deLdnTwUJamFM XJX6oyUjDstdeXRUDtYFqHS4+ctx90pzYqmsjN8Mz72N09cnWjmXZ15swI+HeaLcBN zDmMSwrguMd+oGw1hZq5OkLN5G2bag1s9s9cW9kkywo49SsROBsCqu2zALVoCjpq56 ri1ZUbZSgSLvSQwSt9Y6V7e2xyU9OPcVrKR1pFa6nmklaiBlQkwDdx8HpNC81pks+9 5SfQ9WJ2Dyxxw== From: Sasha Levin To: stable@vger.kernel.org Cc: Daeho Jeong , stable@kernel.org, Chao Yu , Jaegeuk Kim , Sasha Levin Subject: [PATCH 6.6.y 2/2] f2fs: disallow mmap write and data-modifying fallocate on atomic files Date: Tue, 10 Nov 2026 12:42:30 -0500 Message-ID: <20261110173914.2972639-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261110173914.2972639-1-sashal@kernel.org> References: <20261107053447-failed-6.6-06dfe4a7eb69@kernel.org> <20261110173914.2972639-1-sashal@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 Signed-off-by: Sasha Levin --- fs/f2fs/file.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 42eb530cca9f5..79bc005ff4d4c 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -178,6 +178,17 @@ 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 folios and setting FI_ATOMIC_FILE, so either it sees + * our dirty folio and writes it back, or we see the flag. + */ + if (unlikely(f2fs_is_atomic_file(inode))) { + err = -EOPNOTSUPP; + goto out_sem; + } + folio_lock(folio); /* * A concurrent buffered write can extend isize, so we store isize in a @@ -1996,9 +2007,11 @@ 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; @@ -2282,6 +2295,8 @@ static int f2fs_ioc_start_atomic_write(struct file *filp, bool truncate) f2fs_down_write(&fi->i_gc_rwsem[WRITE]); f2fs_down_write(&fi->i_gc_rwsem[READ]); + /* 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 @@ -2337,6 +2352,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp, bool truncate) f2fs_i_size_write(fi->cow_inode, isize); out_unlock: + filemap_invalidate_unlock(inode->i_mapping); f2fs_up_write(&fi->i_gc_rwsem[READ]); f2fs_up_write(&fi->i_gc_rwsem[WRITE]); if (ret) -- 2.53.0