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6c537b845c
find_skb() falls back to np->skb_pool when the GFP_ATOMIC alloc_skb()
fails. The pool is refilled by refill_skbs(), which always allocates
buffers of MAX_SKB_SIZE (ethhdr + iphdr + udphdr + MAX_UDP_CHUNK ==
1502 bytes).
netconsole, however, computes the requested length dynamically as
total_len + np->dev->needed_tailroom
If the egress device declares a non-zero needed_tailroom (e.g. some
tunnel or hardware accelerator devices), the required length can exceed
MAX_SKB_SIZE. The pooled skb is then handed back to the caller, which
immediately performs skb_put(skb, len), trips the tail > end check, and
triggers skb_over_panic().
Leave the normal alloc_skb(len, GFP_ATOMIC) path untouched -- the slab
allocator can still satisfy oversized requests when memory is available,
so senders to devices with non-zero needed_tailroom keep working in the
common case. Only the pool fallback is gated: when alloc_skb() failed
and len exceeds the pool buffer size, skip the skb_dequeue() instead of
burning a pre-allocated skb on a request that would later trip
skb_over_panic(). Reserving pool entries for requests they can actually
satisfy also keeps the panic path, which depends on the pool being
primed, intact.
When that drop happens, emit a rate-limited net_warn() so the user
notices that netconsole is unable to push messages on the egress device.
The warn is skipped under in_nmi() for the same reason schedule_work()
is: printk machinery taken by net_warn_ratelimited() is not NMI-safe and
would risk recursing into the same nbcon console we are servicing.
MAX_SKB_SIZE / MAX_UDP_CHUNK were private to net/core/netpoll.c. Move
them to include/linux/netpoll.h so netconsole can reference the same
definition that refill_skbs() uses, keeping the two in sync by
construction. The header now pulls in <linux/ip.h> and <linux/udp.h>
explicitly so MAX_SKB_SIZE remains self-contained for any future user.
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260604-netcons_fix_before_move-v3-2-ab055b3a6aa5@debian.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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|---|---|---|
| .. | ||
| bpf_sk_storage.c | ||
| datagram.c | ||
| dev_addr_lists_test.c | ||
| dev_addr_lists.c | ||
| dev_api.c | ||
| dev_ioctl.c | ||
| dev.c | ||
| dev.h | ||
| devmem.c | ||
| devmem.h | ||
| drop_monitor.c | ||
| dst_cache.c | ||
| dst.c | ||
| failover.c | ||
| fib_notifier.c | ||
| fib_rules.c | ||
| filter.c | ||
| flow_dissector.c | ||
| flow_offload.c | ||
| gen_estimator.c | ||
| gen_stats.c | ||
| gro_cells.c | ||
| gro.c | ||
| gso.c | ||
| hotdata.c | ||
| hwbm.c | ||
| ieee8021q_helpers.c | ||
| link_watch.c | ||
| lock_debug.c | ||
| lwt_bpf.c | ||
| lwtunnel.c | ||
| Makefile | ||
| mp_dmabuf_devmem.h | ||
| neighbour.c | ||
| net_namespace.c | ||
| net_test.c | ||
| net-procfs.c | ||
| net-sysfs.c | ||
| net-sysfs.h | ||
| net-traces.c | ||
| netclassid_cgroup.c | ||
| netdev_config.c | ||
| netdev_queues.c | ||
| netdev_rx_queue.c | ||
| netdev-genl-gen.c | ||
| netdev-genl-gen.h | ||
| netdev-genl.c | ||
| netevent.c | ||
| netmem_priv.h | ||
| netpoll.c | ||
| netprio_cgroup.c | ||
| of_net.c | ||
| page_pool_priv.h | ||
| page_pool_user.c | ||
| page_pool.c | ||
| pktgen.c | ||
| ptp_classifier.c | ||
| rtnetlink.c | ||
| scm.c | ||
| secure_seq.c | ||
| selftests.c | ||
| skb_fault_injection.c | ||
| skbuff.c | ||
| skmsg.c | ||
| sock_diag.c | ||
| sock_map.c | ||
| sock_reuseport.c | ||
| sock.c | ||
| stream.c | ||
| sysctl_net_core.c | ||
| timestamping.c | ||
| tso.c | ||
| utils.c | ||
| xdp.c | ||