CVE-2026-89973

In the Linux kernel, the following vulnerability has been resolved:

nvme-tcp: check the data direction of a C2HData PDU

nvme_tcp_handle_c2h_data() finds the request by command id and checks
that it has a payload, but it does not check that the command asked for
data to be read.  A controller that answers a write command with C2HData
therefore reaches nvme_tcp_recv_data(), where _copy_to_iter() hits
WARN_ON_ONCE(i->data_source) and returns 0.  The receive path turns that
into -EFAULT and resets the controller.

No data is copied, so this is not memory corruption.  What a controller
gets is a kernel warning it can raise at will, which is fatal on a host
booted with panic_on_warn.

The send path already knows the direction - it consults rq_data_dir()
when it builds a command - and nvme_tcp_handle_r2t() checks the length
and the offset of the request it names.  The C2HData path does not check
the direction at all.

Reject a C2HData PDU whose command is not a read.  Rejecting it fails
the command and resets the controller, as the neighbouring check in this
function does; what goes away is the warning.

  [    6.885580] ------------[ cut here ]------------
  [    6.886457] WARNING: lib/iov_iter.c:193 at _copy_to_iter+0x289/0x1330, CPU#0: kworker/0:1H/71
  [    6.888137] CPU: 0 UID: 0 PID: 71 Comm: kworker/0:1H Not tainted 7.2.0-rc5-NVMETCP-gf5098b6bae76 #1 PREEMPT(lazy)
  [    6.891165] Workqueue: nvme_tcp_wq nvme_tcp_io_work
  [    6.891875] RIP: 0010:_copy_to_iter+0x289/0x1330
  [    6.903739] Call Trace:
  [    6.904085]  <TASK>
  [    6.909254]  __skb_datagram_iter+0x433/0x820
  [    6.911026]  skb_copy_datagram_iter+0x37/0x120
  [    6.911622]  nvme_tcp_recv_skb+0xa07/0x4320
  [    6.913378]  __tcp_read_sock+0x1ab/0x810
  [    6.915788]  nvme_tcp_try_recv+0x152/0x1e0
  [    6.918222]  nvme_tcp_io_work+0x1e4/0x6c0
  [    6.926906]  </TASK>
  [    6.927226] ---[ end trace 0000000000000000 ]---
  [    6.927878] nvme nvme0: queue 1 failed to copy request 0x71 data
  [    6.928709] nvme nvme0: receive failed:  -14