kernel/linux.git/net/core/netpoll.c, branch v6.12.92

netpoll: pass buffer size to egress_dev() to avoid MAC truncation

2026-05-23T11:04:58+00:00

[ Upstream commit 76b93a8107574006b25495664304ea9237494d70 ] egress_dev() formats np->dev_mac via snprintf() but receives buf as a bare char *, so it cannot derive the buffer size from the pointer. The size argument was hardcoded to MAC_ADDR_STR_LEN (3 * ETH_ALEN - 1 = 17), which is silly wrong in two ways: 1) misleading kernel log output on the MAC-selected target path (np->dev_name[0] == '\0'); for example "aa:bb:cc:dd:ee:ff doesn't exist, aborting" was logged as "aa:bb:cc:dd:ee:f doesn't exist, aborting". 2) the second argument of snprintf is the size of the buffer, not the size of what you want to write. Add a bufsz parameter to egress_dev() and pass sizeof(buf) from each caller, matching the standard snprintf() idiom and removing the hardcoded size from the helper. Every caller already declares "char buf[MAC_ADDR_STR_LEN + 1]" so the formatted MAC continues to fit. Tested by booting with netconsole=6665@/aa:bb:cc:dd:ee:ff,6666@10.0.0.1/00:11:22:33:44:55 on a kernel without a matching device. Pre-fix dmesg shows "aa:bb:cc:dd:ee:f doesn't exist, aborting"; post-fix shows the full "aa:bb:cc:dd:ee:ff doesn't exist, aborting". Fixes: f8a10bed32f5 ("netconsole: allow selection of egress interface via MAC address") Cc: stable@vger.kernel.org Signed-off-by: Breno Leitao Link: https://patch.msgid.link/20260501-netpoll_snprintf_fix-v1-1-84b0566e6597@debian.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

netpoll: Extract IPv6 address retrieval function

2026-05-23T11:04:58+00:00

[ Upstream commit 6ad7969a361cbec5822285fb39203678ff462b64 ] Extract the IPv6 address retrieval logic from netpoll_setup() into a dedicated helper function netpoll_take_ipv6() to improve code organization and readability. The function handles obtaining the local IPv6 address from the network device, including proper address type matching between local and remote addresses (link-local vs global), and includes appropriate error handling when IPv6 is not supported or no suitable address is available. Signed-off-by: Breno Leitao Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250618-netpoll_ip_ref-v1-3-c2ac00fe558f@debian.org Signed-off-by: Jakub Kicinski Stable-dep-of: 76b93a810757 ("netpoll: pass buffer size to egress_dev() to avoid MAC truncation") Signed-off-by: Sasha Levin

netpoll: fix IPv6 local-address corruption

2026-05-23T11:04:54+00:00

[ Upstream commit 3bc179bc7146c26c9dff75d2943d10528274e301 ] netpoll_setup() decides whether to auto-populate the local source address by testing np->local_ip.ip, which only inspects the first 4 bytes of the union inet_addr storage. For an IPv6 netpoll whose caller-supplied local address has a zero high-32 bits (::1, ::, IPv4-mapped ::ffff:a.b.c.d, etc.), this misdetects the address as unset (which they are not, but the first 4 bytes are empty), calls netpoll_take_ipv6() and overwrites it with whatever matching link-local/global address the device happens to expose first. Introduce a helper netpoll_local_ip_unset() that picks the correct family-aware test (ipv6_addr_any() for IPv6, !.ip for IPv4) and use it from netpoll_setup(). Reproducer is something like: echo "::2" > local_ip echo 1 > enabled cat local_ip # before this fix: 2001:db8::1 (caller-supplied ::2 was clobbered) # after this fix: ::2 Fixes: b7394d2429c1 ("netpoll: prepare for ipv6") Signed-off-by: Breno Leitao Link: https://patch.msgid.link/20260424-netpoll_fix-v1-1-3a55348c625f@debian.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

netpoll: extract IPv4 address retrieval into helper function

2026-05-23T11:04:54+00:00

[ Upstream commit 3699f992e8c22d3ce54d2c1a5774e2c49028f99c ] Move the IPv4 address retrieval logic from netpoll_setup() into a separate netpoll_take_ipv4() function to improve code organization and readability. This change consolidates the IPv4-specific logic and error handling into a dedicated function while maintaining the same functionality. No functional changes. Signed-off-by: Breno Leitao Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250618-netpoll_ip_ref-v1-2-c2ac00fe558f@debian.org Signed-off-by: Jakub Kicinski Stable-dep-of: 3bc179bc7146 ("netpoll: fix IPv6 local-address corruption") Signed-off-by: Sasha Levin

netpoll: Extract carrier wait function

2026-05-23T11:04:54+00:00

[ Upstream commit 76d30b51e818064e02917ce6328fb2c8adce5c87 ] Extract the carrier waiting logic into a dedicated helper function netpoll_wait_carrier() to improve code readability and reduce duplication in netpoll_setup(). Signed-off-by: Breno Leitao Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250618-netpoll_ip_ref-v1-1-c2ac00fe558f@debian.org Signed-off-by: Jakub Kicinski Stable-dep-of: 3bc179bc7146 ("netpoll: fix IPv6 local-address corruption") Signed-off-by: Sasha Levin

netconsole: allow selection of egress interface via MAC address

2026-05-23T11:04:54+00:00

[ Upstream commit f8a10bed32f5fbede13a5f22fdc4ab8740ea213a ] Currently, netconsole has two methods of configuration - module parameter and configfs. The former interface allows for netconsole activation earlier during boot (by specifying the module parameter on the kernel command line), so it is preferred for debugging issues which arise before userspace is up/the configfs interface can be used. The module parameter syntax requires specifying the egress interface name. This requirement makes it hard to use for a couple reasons: - The egress interface name can be hard or impossible to predict. For example, installing a new network card in a system can change the interface names assigned by the kernel. - When constructing the module parameter, one may have trouble determining the original (kernel-assigned) name of the interface (which is the name that should be given to netconsole) if some stable interface naming scheme is in effect. A human can usually look at kernel logs to determine the original name, but this is very painful if automation is constructing the parameter. For these reasons, allow selection of the egress interface via MAC address when configuring netconsole using the module parameter. Update the netconsole documentation with an example of the new syntax. Selection of egress interface by MAC address via configfs is far less interesting (since when this interface can be used, one should be able to easily convert between MAC address and interface name), so it is left unimplemented. Signed-off-by: Uday Shankar Reviewed-by: Breno Leitao Tested-by: Breno Leitao Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250312-netconsole-v6-2-3437933e79b8@purestorage.com Signed-off-by: Paolo Abeni Stable-dep-of: 3bc179bc7146 ("netpoll: fix IPv6 local-address corruption") Signed-off-by: Sasha Levin

net: netpoll: ensure skb_pool list is always initialized

2025-11-24T09:36:08+00:00

commit f0d0277796db613c124206544b6dbe95b520ab6c upstream. 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 Signed-off-by: Greg Kroah-Hartman

net: netpoll: fix incorrect refcount handling causing incorrect cleanup

2025-11-24T09:36:06+00:00

[ Upstream commit 49c8d2c1f94cc2f4d1a108530d7ba52614b874c2 ] commit efa95b01da18 ("netpoll: fix use after free") incorrectly ignored the refcount and prematurely set dev->npinfo to NULL during netpoll cleanup, leading to improper behavior and memory leaks. Scenario causing lack of proper cleanup: 1) A netpoll is associated with a NIC (e.g., eth0) and netdev->npinfo is allocated, and refcnt = 1 - Keep in mind that npinfo is shared among all netpoll instances. In this case, there is just one. 2) Another netpoll is also associated with the same NIC and npinfo->refcnt += 1. - Now dev->npinfo->refcnt = 2; - There is just one npinfo associated to the netdev. 3) When the first netpolls goes to clean up: - The first cleanup succeeds and clears np->dev->npinfo, ignoring refcnt. - It basically calls `RCU_INIT_POINTER(np->dev->npinfo, NULL);` - Set dev->npinfo = NULL, without proper cleanup - No ->ndo_netpoll_cleanup() is either called 4) Now the second target tries to clean up - The second cleanup fails because np->dev->npinfo is already NULL. * In this case, ops->ndo_netpoll_cleanup() was never called, and the skb pool is not cleaned as well (for the second netpoll instance) - This leaks npinfo and skbpool skbs, which is clearly reported by kmemleak. Revert commit efa95b01da18 ("netpoll: fix use after free") and adds clarifying comments emphasizing that npinfo cleanup should only happen once the refcount reaches zero, ensuring stable and correct netpoll behavior. Cc: # 3.17.x Cc: Jay Vosburgh Fixes: efa95b01da18 ("netpoll: fix use after free") Signed-off-by: Breno Leitao Reviewed-by: Simon Horman Link: https://patch.msgid.link/20251107-netconsole_torture-v10-1-749227b55f63@debian.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

net: netpoll: flush skb pool during cleanup

2025-11-24T09:36:06+00:00

[ Upstream commit 6c59f16f1770481a6ee684720ec55b1e38b3a4b2 ] 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 Stable-dep-of: 49c8d2c1f94c ("net: netpoll: fix incorrect refcount handling causing incorrect cleanup") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

net: netpoll: Individualize the skb pool

2025-11-24T09:36:06+00:00

[ Upstream commit 221a9c1df790fa711d65daf5ba05d0addc279153 ] 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 Stable-dep-of: 49c8d2c1f94c ("net: netpoll: fix incorrect refcount handling causing incorrect cleanup") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman