[PATCH net v4 0/2] gve: fix RX page refcount overflow with the pagecnt bias

[Amaan Cheval <amaan.cheval@gmail.com>]

gve's GQI and DQO-QPL RX paths bias every RX page's refcount to INT_MAX,
so a single get_page() from the stack, e.g. splice() of received data,
overflows it: splice/tee fail with EIO/EFAULT and GQI can reset the
NIC. Patch 2 lowers the bias to USHRT_MAX, as other drivers do.

With the smaller bias the driver gives up its last reference on a page
once every USHRT_MAX handoffs instead of once every INT_MAX, which is
only safe while every consumer holds its reference until the buffer is
recycled. That is not the case for an XDP_REDIRECT from DQO-QPL to an
AF_XDP socket in copy mode, a path the driver never meant to support:
commit d8a8ca14c937 dropped the queue_format check that used to refuse
it. Patch 1 restores that check for DQO-QPL, so patch 2 depends on it.
Trees before 6.17 still have the old check, so there patch 2 stands
alone.

Harshitha mentioned on v2 that Google would send a patch blocking XDP
on DQO-QPL; if one is already in flight I'm happy to drop patch 1 in
its favour.

v4:
 - Add patch 1/2 blocking XDP on DQO-QPL (Sashiko).
 - Say "overflow" instead of "headroom"; use USHRT_MAX directly instead
   of a macro (Maciej).
 - Say which trees need patch 1, for stable.
v3: https://lore.kernel.org/netdev/20261103090651.35399-1-amaan.cheval@gmail.com/
v2: https://lore.kernel.org/netdev/20261102112613.18334-1-amaan.cheval@gmail.com/
v1: https://lore.kernel.org/netdev/20261031173449.2439047-1-amaan.cheval@gmail.com/


Amaan Cheval (2):
  gve: block XDP on the DQO-QPL queue format
  gve: fix RX page refcount overflow from the pagecnt bias

 drivers/net/ethernet/google/gve/gve.h                |  2 +-
 .../net/ethernet/google/gve/gve_buffer_mgmt_dqo.c    |  4 ++--
 drivers/net/ethernet/google/gve/gve_main.c           |  6 ++++++
 drivers/net/ethernet/google/gve/gve_rx.c             |  8 ++++----
 drivers/net/ethernet/google/gve/gve_utils.c          | 12 ++++--------
 drivers/net/ethernet/google/gve/gve_utils.h          |  2 +-
 6 files changed, 18 insertions(+), 16 deletions(-)


base-commit: 21f57ec673a1917547c808cfa81890485fffa03b
-- 
2.47.3