Subject: [PATCH net v3 0/3] Stop corrupting socket's task_frag

From: Benjamin Coddington <[email-masked]>
Date: Tue, 13 Dec 2022 06:10:36 -0500

The networking code uses flags in sk_allocation to determine if it can use
current->task_frag, however in-kernel users of sockets may stop setting
sk_allocation when they convert to the preferred memalloc_nofs_save/restore,
as SUNRPC has done in commit a1231fda7e94 ("SUNRPC: Set memalloc_nofs_save()
on all rpciod/xprtiod jobs").

This will cause corruption in current->task_frag when recursing into the
network layer for those subsystems during page fault or reclaim.  The
corruption is difficult to diagnose because stack traces may not contain the
offending subsystem at all.  The corruption is unlikely to show up in
testing because it requires memory pressure, and so subsystems that
convert to memalloc_nofs_save/restore are likely to continue to run into
this issue.

Previous reports and proposed fixes:
https://lore.kernel.org/netdev/[email-masked]/
https://lore.kernel.org/netdev/[email-masked]/
https://lore.kernel.org/linux-nfs/[email-masked]/

Guilluame Nault has done all of the hard work tracking this problem down and
finding the best fix for this issue.  I'm just taking a turn posting another
fix.

Changes on v2:
	- rebased on -net
	- set sk_use_task_frag = false for xfrm/espintcp.c

Changes on v3:
	- fixup comments in sock.h for kernel-doc

Benjamin Coddington (2):
  Treewide: Stop corrupting socket's task_frag
  net: simplify sk_page_frag

Guillaume Nault (1):
  net: Introduce sk_use_task_frag in struct sock.

 drivers/block/drbd/drbd_receiver.c |  3 +++
 drivers/block/nbd.c                |  1 +
 drivers/nvme/host/tcp.c            |  1 +
 drivers/scsi/iscsi_tcp.c           |  1 +
 drivers/usb/usbip/usbip_common.c   |  1 +
 fs/afs/rxrpc.c                     |  1 +
 fs/cifs/connect.c                  |  1 +
 fs/dlm/lowcomms.c                  |  2 ++
 fs/ocfs2/cluster/tcp.c             |  1 +
 include/net/sock.h                 | 10 ++++++----
 net/9p/trans_fd.c                  |  1 +
 net/ceph/messenger.c               |  1 +
 net/core/sock.c                    |  1 +
 net/sunrpc/xprtsock.c              |  3 +++
 net/xfrm/espintcp.c                |  1 +
 15 files changed, 25 insertions(+), 4 deletions(-)

-- 
2.31.1