* Patch "netfs: Fix unbuffered write error handling" has been added to the 6.12-stable tree
2025-08-22 3:08 ` [PATCH 6.12.y] netfs: Fix unbuffered write error handling Sasha Levin
@ 2025-08-22 6:24 ` gregkh
0 siblings, 0 replies; 2+ messages in thread
From: gregkh @ 2025-08-22 6:24 UTC (permalink / raw)
To: brauner, dhowells, fengxiaoli0714, gregkh, netfs, pc, sashal,
sfrench, sprasad
Cc: stable-commits
This is a note to let you know that I've just added the patch titled
netfs: Fix unbuffered write error handling
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netfs-fix-unbuffered-write-error-handling.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.
From stable+bounces-172251-greg=kroah.com@vger.kernel.org Fri Aug 22 05:09:26 2025
From: Sasha Levin <sashal@kernel.org>
Date: Thu, 21 Aug 2025 23:08:00 -0400
Subject: netfs: Fix unbuffered write error handling
To: stable@vger.kernel.org
Cc: David Howells <dhowells@redhat.com>, Xiaoli Feng <fengxiaoli0714@gmail.com>, Paulo Alcantara <pc@manguebit.org>, Steve French <sfrench@samba.org>, Shyam Prasad N <sprasad@microsoft.com>, netfs@lists.linux.dev, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, Christian Brauner <brauner@kernel.org>, Sasha Levin <sashal@kernel.org>
Message-ID: <20250822030800.1054685-1-sashal@kernel.org>
From: David Howells <dhowells@redhat.com>
[ 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 <fengxiaoli0714@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220445
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/915443.1755207950@warthog.procyon.org.uk
cc: Paulo Alcantara <pc@manguebit.org>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <sprasad@microsoft.com>
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 <brauner@kernel.org>
[ Dropped read_collect.c hunk ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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(-)
--- a/fs/netfs/write_collect.c
+++ b/fs/netfs/write_collect.c
@@ -433,6 +433,7 @@ reassess_streams:
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(struc
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(struc
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 &&
--- a/fs/netfs/write_issue.c
+++ b/fs/netfs/write_issue.c
@@ -115,12 +115,12 @@ struct netfs_io_request *netfs_create_wr
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;
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -744,6 +744,9 @@ iter_file_splice_write(struct pipe_inode
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;
--- 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 */
};
/*
Patches currently in stable-queue which might be from sashal@kernel.org are
queue-6.12/btrfs-send-use-fallocate-for-hole-punching-with-send-stream-v2.patch
queue-6.12/usb-typec-fusb302-cache-pd-rx-state.patch
queue-6.12/btrfs-move-transaction-aborts-to-the-error-site-in-add_block_group_free_space.patch
queue-6.12/btrfs-send-avoid-path-allocation-for-the-current-inode-when-issuing-commands.patch
queue-6.12/btrfs-send-keep-the-current-inode-s-path-cached.patch
queue-6.12/btrfs-abort-transaction-on-unexpected-eb-generation-at-btrfs_copy_root.patch
queue-6.12/btrfs-always-abort-transaction-on-failure-to-add-block-group-to-free-space-tree.patch
queue-6.12/btrfs-zoned-requeue-to-unused-block-group-list-if-zone-finish-failed.patch
queue-6.12/btrfs-explicitly-ref-count-block_group-on-new_bgs-list.patch
queue-6.12/serial-8250-fix-panic-due-to-pslverr.patch
queue-6.12/xfs-fully-decouple-xfs_ibulk-flags-from-xfs_iwalk-flags.patch
queue-6.12/btrfs-qgroup-drop-unused-parameter-fs_info-from-__del_qgroup_rb.patch
queue-6.12/btrfs-send-make-fs_path_len-inline-and-constify-its-argument.patch
queue-6.12/netfs-fix-unbuffered-write-error-handling.patch
queue-6.12/usb-typec-use-str_enable_disable-like-helpers.patch
queue-6.12/btrfs-send-add-and-use-helper-to-rename-current-inode-when-processing-refs.patch
queue-6.12/btrfs-send-only-use-boolean-variables-at-process_recorded_refs.patch
queue-6.12/btrfs-qgroup-fix-race-between-quota-disable-and-quota-rescan-ioctl.patch
queue-6.12/btrfs-send-factor-out-common-logic-when-sending-xattrs.patch
queue-6.12/btrfs-codify-pattern-for-adding-block_group-to-bg_list.patch
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