From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 28BD92652B4; Fri, 22 Aug 2025 03:08:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755832084; cv=none; b=erxwrKxigNrMCX/7tYXeO0K1diU7JsUWvZwA/PHT1PfRUlYDbXVQlmZLWhkVe7eS6MYmpHFCYxvdzOsSU1SjfQpUzk3NKh7SzEX2Hqr4emB2wK+uVRxNf4BlcrzJs8oeova21l5rThgdO71/NerImhmxVF4qIviT5q4OGjTaUMM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755832084; c=relaxed/simple; bh=SCWJsd9vjE1VJ9L3wefl1VGRbBT52yKi9plp6KLTV/M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pemkkggPRbPeP8RGGkaO9Pgfy+KK3/FagthQ0cXR9uA28eOkU79IEJJKmDwyeD1QZl8ca2m/A0guWEihPUfnjA0YQogsFtzMLMrRQXJxjF1/H/C8hxSaxZ2siNlc/SIBjO+pXFt2xqSFcpd/JzJp6Fg69UKGFKgZC4e3PTbzohI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pq826WrM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pq826WrM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1398C4CEEB; Fri, 22 Aug 2025 03:08:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755832084; bh=SCWJsd9vjE1VJ9L3wefl1VGRbBT52yKi9plp6KLTV/M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pq826WrMct/ELjpuRCD360hXL5d6eRZjJlhvi1ZvcFso6C915lRq4I8Y/MQvxFvuk c61/R4JqIAiKBru31s6kf8r+L9NUyoUKZCg6JNEZe0OcRQuHHIMqM/76MFRuT22g53 EvSqtDBdC+41GoPOdTB132X/U0RD6+K8MlKPfINpB+ZXjeAXb553Z4Sm5j5PG3Gy3X lC1UGWW/biRSQpqlW/VV98IVGwveT907OhGljIOMQ0ZFb9OvETPWO4iIzZwUjETta/ neRSqnMgpnVKPZyGmhuL1i4ab5jXoogzvcbjqSkVXHBUNsTIryEqKRjwSDMQcl9deU FAFNC8olFBgiQ== From: Sasha Levin To: stable@vger.kernel.org Cc: David Howells , Xiaoli Feng , Paulo Alcantara , Steve French , Shyam Prasad N , netfs@lists.linux.dev, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christian Brauner , Sasha Levin Subject: [PATCH 6.12.y] netfs: Fix unbuffered write error handling Date: Thu, 21 Aug 2025 23:08:00 -0400 Message-ID: <20250822030800.1054685-1-sashal@kernel.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <2025082157-dedicator-hurled-4d65@gregkh> References: <2025082157-dedicator-hurled-4d65@gregkh> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: David Howells [ Upstream commit a3de58b12ce074ec05b8741fa28d62ccb1070468 ] If all the subrequests in an unbuffered write stream fail, the subrequest collector doesn't update the stream->transferred value and it retains its initial LONG_MAX value. Unfortunately, if all active streams fail, then we take the smallest value of { LONG_MAX, LONG_MAX, ... } as the value to set in wreq->transferred - which is then returned from ->write_iter(). LONG_MAX was chosen as the initial value so that all the streams can be quickly assessed by taking the smallest value of all stream->transferred - but this only works if we've set any of them. Fix this by adding a flag to indicate whether the value in stream->transferred is valid and checking that when we integrate the values. stream->transferred can then be initialised to zero. This was found by running the generic/750 xfstest against cifs with cache=none. It splices data to the target file. Once (if) it has used up all the available scratch space, the writes start failing with ENOSPC. This causes ->write_iter() to fail. However, it was returning wreq->transferred, i.e. LONG_MAX, rather than an error (because it thought the amount transferred was non-zero) and iter_file_splice_write() would then try to clean up that amount of pipe bufferage - leading to an oops when it overran. The kernel log showed: CIFS: VFS: Send error in write = -28 followed by: BUG: kernel NULL pointer dereference, address: 0000000000000008 with: RIP: 0010:iter_file_splice_write+0x3a4/0x520 do_splice+0x197/0x4e0 or: RIP: 0010:pipe_buf_release (include/linux/pipe_fs_i.h:282) iter_file_splice_write (fs/splice.c:755) Also put a warning check into splice to announce if ->write_iter() returned that it had written more than it was asked to. Fixes: 288ace2f57c9 ("netfs: New writeback implementation") Reported-by: Xiaoli Feng Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220445 Signed-off-by: David Howells Link: https://lore.kernel.org/915443.1755207950@warthog.procyon.org.uk cc: Paulo Alcantara cc: Steve French cc: Shyam Prasad N cc: netfs@lists.linux.dev cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: stable@vger.kernel.org Signed-off-by: Christian Brauner [ Dropped read_collect.c hunk ] Signed-off-by: Sasha Levin --- fs/netfs/write_collect.c | 10 ++++++++-- fs/netfs/write_issue.c | 4 ++-- fs/splice.c | 3 +++ include/linux/netfs.h | 1 + 4 files changed, 14 insertions(+), 4 deletions(-) diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c index a968688a7323..c349867d74c3 100644 --- a/fs/netfs/write_collect.c +++ b/fs/netfs/write_collect.c @@ -433,6 +433,7 @@ static void netfs_collect_write_results(struct netfs_io_request *wreq) if (front->start + front->transferred > stream->collected_to) { stream->collected_to = front->start + front->transferred; stream->transferred = stream->collected_to - wreq->start; + stream->transferred_valid = true; notes |= MADE_PROGRESS; } if (test_bit(NETFS_SREQ_FAILED, &front->flags)) { @@ -538,6 +539,7 @@ void netfs_write_collection_worker(struct work_struct *work) struct netfs_io_request *wreq = container_of(work, struct netfs_io_request, work); struct netfs_inode *ictx = netfs_inode(wreq->inode); size_t transferred; + bool transferred_valid = false; int s; _enter("R=%x", wreq->debug_id); @@ -568,12 +570,16 @@ void netfs_write_collection_worker(struct work_struct *work) netfs_put_request(wreq, false, netfs_rreq_trace_put_work); return; } - if (stream->transferred < transferred) + if (stream->transferred_valid && + stream->transferred < transferred) { transferred = stream->transferred; + transferred_valid = true; + } } /* Okay, declare that all I/O is complete. */ - wreq->transferred = transferred; + if (transferred_valid) + wreq->transferred = transferred; trace_netfs_rreq(wreq, netfs_rreq_trace_write_done); if (wreq->io_streams[1].active && diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c index bf6d507578e5..b7830a15ae40 100644 --- a/fs/netfs/write_issue.c +++ b/fs/netfs/write_issue.c @@ -115,12 +115,12 @@ struct netfs_io_request *netfs_create_write_req(struct address_space *mapping, wreq->io_streams[0].prepare_write = ictx->ops->prepare_write; wreq->io_streams[0].issue_write = ictx->ops->issue_write; wreq->io_streams[0].collected_to = start; - wreq->io_streams[0].transferred = LONG_MAX; + wreq->io_streams[0].transferred = 0; wreq->io_streams[1].stream_nr = 1; wreq->io_streams[1].source = NETFS_WRITE_TO_CACHE; wreq->io_streams[1].collected_to = start; - wreq->io_streams[1].transferred = LONG_MAX; + wreq->io_streams[1].transferred = 0; if (fscache_resources_valid(&wreq->cache_resources)) { wreq->io_streams[1].avail = true; wreq->io_streams[1].active = true; diff --git a/fs/splice.c b/fs/splice.c index 38f8c9426731..ed8177f6d620 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -744,6 +744,9 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out, sd.pos = kiocb.ki_pos; if (ret <= 0) break; + WARN_ONCE(ret > sd.total_len - left, + "Splice Exceeded! ret=%zd tot=%zu left=%zu\n", + ret, sd.total_len, left); sd.num_spliced += ret; sd.total_len -= ret; diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 474481ee8b7c..83d313718cd5 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -150,6 +150,7 @@ struct netfs_io_stream { bool active; /* T if stream is active */ bool need_retry; /* T if this stream needs retrying */ bool failed; /* T if this stream failed */ + bool transferred_valid; /* T is ->transferred is valid */ }; /* -- 2.50.1