linux.git/net/core/netpoll.c, branch v6.14

netpoll: hold rcu read lock in __netpoll_send_skb()

2025-03-08T03:57:33+00:00

The function __netpoll_send_skb() is being invoked without holding the
RCU read lock. This oversight triggers a warning message when
CONFIG_PROVE_RCU_LIST is enabled:

	net/core/netpoll.c:330 suspicious rcu_dereference_check() usage!

	 netpoll_send_skb
	 netpoll_send_udp
	 write_ext_msg
	 console_flush_all
	 console_unlock
	 vprintk_emit

To prevent npinfo from disappearing unexpectedly, ensure that
__netpoll_send_skb() is protected with the RCU read lock.

Fixes: 2899656b494dcd1 ("netpoll: take rcu_read_lock_bh() in netpoll_send_skb_on_dev()")
Signed-off-by: Breno Leitao 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20250306-netpoll_rcu_v2-v2-1-bc4f5c51742a@debian.org
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2025-01-16T18:34:59+00:00

Cross-merge networking fixes after downstream PR (net-6.13-rc8).

Conflicts:

drivers/net/ethernet/realtek/r8169_main.c
  1f691a1fc4be ("r8169: remove redundant hwmon support")
  152d00a91396 ("r8169: simplify setting hwmon attribute visibility")
https://lore.kernel.org/20250115122152.760b4e8d@canb.auug.org.au

Adjacent changes:

drivers/net/ethernet/broadcom/bnxt/bnxt.c
  152f4da05aee ("bnxt_en: add support for rx-copybreak ethtool command")
  f0aa6a37a3db ("eth: bnxt: always recalculate features after XDP clearing, fix null-deref")

drivers/net/ethernet/intel/ice/ice_type.h
  50327223a8bb ("ice: add lock to protect low latency interface")
  dc26548d729e ("ice: Fix quad registers read on E825")

Signed-off-by: Jakub Kicinski

net: netpoll: ensure skb_pool list is always initialized

2025-01-15T01:45:14+00:00

When __netpoll_setup() is called directly, instead of through
netpoll_setup(), the np->skb_pool list head isn't initialized.
If skb_pool_flush() is later called, then we hit a NULL pointer
in skb_queue_purge_reason().  This can be seen with this repro,
when CONFIG_NETCONSOLE is enabled as a module:

    ip tuntap add mode tap tap0
    ip link add name br0 type bridge
    ip link set dev tap0 master br0
    modprobe netconsole netconsole=4444@10.0.0.1/br0,9353@10.0.0.2/
    rmmod netconsole

The backtrace is:

    BUG: kernel NULL pointer dereference, address: 0000000000000008
    #PF: supervisor write access in kernel mode
    #PF: error_code(0x0002) - not-present page
    ... ... ...
    Call Trace:
     
     __netpoll_free+0xa5/0xf0
     br_netpoll_cleanup+0x43/0x50 [bridge]
     do_netpoll_cleanup+0x43/0xc0
     netconsole_netdev_event+0x1e3/0x300 [netconsole]
     unregister_netdevice_notifier+0xd9/0x150
     cleanup_module+0x45/0x920 [netconsole]
     __se_sys_delete_module+0x205/0x290
     do_syscall_64+0x70/0x150
     entry_SYSCALL_64_after_hwframe+0x76/0x7e

Move the skb_pool list setup and initial skb fill into __netpoll_setup().

Fixes: 221a9c1df790 ("net: netpoll: Individualize the skb pool")
Signed-off-by: John Sperbeck 
Reviewed-by: Breno Leitao 
Link: https://patch.msgid.link/20250114011354.2096812-1-jsperbeck@google.com
Signed-off-by: Jakub Kicinski

netpoll: Make netpoll_send_udp return status instead of void

2024-12-05T03:15:38+00:00

netpoll_send_udp can return if send was successful.
It will allow client code to be aware of the send status.

Possible return values are the result of __netpoll_send_skb (cast to int)
and -ENOMEM. This doesn't cover the case when TX was not successful
instantaneously and was scheduled for later, __netpoll__send_skb returns
success in that case.

Signed-off-by: Maksym Kutsevol 
Link: https://patch.msgid.link/20241202-netcons-add-udp-send-fail-statistics-to-netconsole-v5-1-70e82239f922@kutsevol.com
Signed-off-by: Jakub Kicinski

netpoll: Use rtnl_dereference() for npinfo pointer access

2024-12-05T02:41:37+00:00

In the __netpoll_setup() function, when accessing the device's npinfo
pointer, replace rcu_access_pointer() with rtnl_dereference(). This
change is more appropriate, as suggested by Herbert Xu[1].

The function is called with the RTNL mutex held, and the pointer is
being dereferenced later, so, dereference earlier and just reuse the
pointer for the if/else.

The replacement ensures correct pointer access while maintaining
the existing locking and RCU semantics of the netpoll subsystem.

Link: https://lore.kernel.org/lkml/Zz1cKZYt1e7elibV@gondor.apana.org.au/ [1]
Suggested-by: Herbert Xu 
Signed-off-by: Breno Leitao 
Reviewed-by: Jacob Keller 
Acked-by: Herbert Xu 
Link: https://patch.msgid.link/20241202-netpoll_rcu_herbet_fix-v2-1-2b9d58edc76a@debian.org
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2024-11-19T12:56:02+00:00

Merge in late fixes to prepare for the 6.13 net-next PR.

Conflicts:

include/linux/phy.h
  41ffcd95015f net: phy: fix phylib's dual eee_enabled
  721aa69e708b net: phy: convert eee_broken_modes to a linkmode bitmap
https://lore.kernel.org/all/20241118135512.1039208b@canb.auug.org.au/

drivers/net/ethernet/wangxun/txgbe/txgbe_phy.c
  2160428bcb20 net: txgbe: fix null pointer to pcs
  2160428bcb20 net: txgbe: remove GPIO interrupt controller

Adjacent commits:

include/linux/phy.h
  41ffcd95015f net: phy: fix phylib's dual eee_enabled
  516a5f11eb97 net: phy: respect cached advertising when re-enabling EEE

Signed-off-by: Paolo Abeni

netpoll: Use rcu_access_pointer() in __netpoll_setup

2024-11-19T03:01:36+00:00

The ndev->npinfo pointer in __netpoll_setup() is RCU-protected but is being
accessed directly for a NULL check. While no RCU read lock is held in this
context, we should still use proper RCU primitives for consistency and
correctness.

Replace the direct NULL check with rcu_access_pointer(), which is the
appropriate primitive when only checking for NULL without dereferencing
the pointer. This function provides the necessary ordering guarantees
without requiring RCU read-side protection.

Reviewed-by: Michal Kubiak 
Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-1-a1888dcb4a02@debian.org
Signed-off-by: Jakub Kicinski

net: netpoll: flush skb pool during cleanup

2024-11-16T00:25:34+00:00

The netpoll subsystem maintains a pool of 32 pre-allocated SKBs per
instance, but these SKBs are not freed when the netpoll user is brought
down. This leads to memory waste as these buffers remain allocated but
unused.

Add skb_pool_flush() to properly clean up these SKBs when netconsole is
terminated, improving memory efficiency.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20241114-skb_buffers_v2-v3-2-9be9f52a8b69@debian.org
Signed-off-by: Jakub Kicinski

net: netpoll: Individualize the skb pool

2024-11-16T00:25:34+00:00

The current implementation of the netpoll system uses a global skb
pool, which can lead to inefficient memory usage and
waste when targets are disabled or no longer in use.

This can result in a significant amount of memory being unnecessarily
allocated and retained, potentially causing performance issues and
limiting the availability of resources for other system components.

Modify the netpoll system to assign a skb pool to each target instead of
using a global one.

This approach allows for more fine-grained control over memory
allocation and deallocation, ensuring that resources are only allocated
and retained as needed.

Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20241114-skb_buffers_v2-v3-1-9be9f52a8b69@debian.org
Signed-off-by: Jakub Kicinski

netpoll: remove ndo_netpoll_setup() second argument

2024-10-23T11:31:32+00:00

npinfo is not used in any of the ndo_netpoll_setup() methods.

Signed-off-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20241018052108.2610827-1-edumazet@google.com
Signed-off-by: Paolo Abeni