kernel/linux.git/net/packet, branch v6.6.152

packet: synchronize pressure clearing with ring reconfiguration

2026-08-19T16:13:10+00:00

commit 1a35da325cac4d5bcad76a2aa943408a6f1d9000 upstream. packet_set_ring() updates the RX ring state under sk_receive_queue.lock, but used to publish the tpacket receive mode through po->prot_hook.func after releasing that lock. packet_poll() and packet_recvmsg() can then run the pressure clearing path after the ring has been cleared while still seeing tpacket_rcv, causing __packet_rcv_has_room() to dereference stale or NULL ring storage. Move the existing receive hook assignment into the same sk_receive_queue.lock section as the ring state update. Keep the assignment otherwise unchanged, including on TX ring reconfiguration, to avoid adding behavior changes that are not required for the fix. Serialize packet_recvmsg() pressure clearing with the same queue lock only after PACKET_SOCK_PRESSURE has been observed. If the flag is clear and the socket has moved away from tpacket_rcv, packet_set_ring() has already detached the socket and waited for synchronize_net(), so no new packet input can set the flag again. packet_poll() already holds sk_receive_queue.lock, so it uses the new unlocked helper directly. Fixes: 2ccdbaa6d55b ("packet: rollover lock contention avoidance") Cc: stable@vger.kernel.org Reported-by: Vega Assisted-by: Codex:gpt-5.4 Signed-off-by: Zihan Xi Link: https://patch.msgid.link/f90b5688311fa278d1361ea8c6be0bf25967d591.1785247446.git.zihanx@nebusec.ai Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman

net/packet: reset the MAC header on the packet-socket transmit path

2026-08-19T16:13:10+00:00

commit c2707480cfbf19c7619acc9c089d17f20869821f upstream. packet_parse_headers() resets the MAC header only for a SOCK_RAW frame whose socket did not bind a protocol. A protocol-bound SOCK_RAW socket, any SOCK_DGRAM frame, and the legacy SOCK_PACKET path therefore leave skb->mac_header unset here. For frames sent via __dev_queue_xmit() this is harmless: it resets the MAC header unconditionally. But the packet-socket PACKET_QDISC_BYPASS path uses dev_direct_xmit(), which does not, so the frame reaches ndo_start_xmit() with the MAC header unset. A driver that reads eth_hdr(skb) on transmit then dereferences skb->head + (u16)~0, an out-of-bounds access ~64 KiB past the head -- the same class fixed for one consumer in commit f5089008f90c ("macsec: do not read an unset MAC header in macsec_encrypt()"). packet_parse_headers() runs only on the transmit path, where skb->data points at the start of the L2 header for every packet-socket type regardless of its length: SOCK_RAW and SOCK_PACKET carry a user-supplied header and SOCK_DGRAM has one built by dev_hard_header(). Reset the MAC header unconditionally, mirroring __dev_queue_xmit(), so the frame is anchored on the bypass path too. Found by 0sec (https://0sec.ai) using automated source analysis; verified against source and matched to the macsec KASAN report in f5089008f90c. Compile-tested. Fixes: 75c65772c3d1 ("net/packet: Ask driver for protocol if not provided by user") Cc: stable@vger.kernel.org Signed-off-by: Doruk Tan Ozturk Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260724144015.63219-1-doruk@0sec.ai Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

packet: use consistent hard_header_len in TX_RING send path

2026-08-19T16:13:10+00:00

commit 21b5953e7494c16a42e6cd8cf110e18d13ae4a6b upstream. tpacket_snd() reads dev->hard_header_len independently for skb allocation and header construction in tpacket_fill_skb(). Concurrent netdevice reconfiguration can therefore make the reserved headroom smaller than the amount later pushed, or make copylen - hard_header_len negative. Snapshot hard_header_len once before processing ring frames and use it for the frame limit, headroom allocation, copy length, and skb construction. Pass the snapshot to tpacket_fill_skb(). The separate SOCK_DGRAM consistency problem between hard_header_len and header_ops->create is not addressed here. Fixes: 69e3c75f4d54 ("net: TX_RING and packet mmap") Cc: stable@vger.kernel.org Signed-off-by: Qihang Tang Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260805125729.19220-4-q.h.hack.winter@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

packet: use consistent hard_header_len in non-ring send paths

2026-08-19T16:13:09+00:00

commit 03390aa32e669cc4ecd7d34108e2e1afc13d689d upstream. packet_snd() reads dev->hard_header_len multiple times while allocating and constructing an skb. Device reconfiguration can change this value concurrently, for example through bonding device type changes. For SOCK_RAW, packet_snd() can save a larger value in reserve and later allocate headroom using a smaller value. Moving skb->data back by reserve then places it before skb->head, and the following copy from userspace can attempt an out-of-bounds write. packet_sendmsg_spkt() has the same issue because it calculates its reservation and header offset from separate reads before dropping the RCU read lock to allocate the skb. Add LL_RESERVED_SPACE_EX() for callers that already saved a header length. Read hard_header_len once in packet_snd() and use it for allocation and construction. In packet_sendmsg_spkt(), preserve the allocation-time value through the device lookup retry. The separate SOCK_DGRAM consistency problem between hard_header_len and header_ops->create is not addressed here. Fixes: b84bbaf7a6c8 ("packet: in packet_snd start writing at link layer allocation") Cc: stable@vger.kernel.org Signed-off-by: Qihang Tang Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260805125729.19220-3-q.h.hack.winter@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

net/packet: avoid fanout hook re-registration after unregister

2026-08-03T09:15:19+00:00

[ Upstream commit 50aff80475abd3533eef4320477037e6fcc6b56e ] packet_set_ring() temporarily detaches a socket from packet delivery while reconfiguring its ring. It records the previous running state, clears po->num, unregisters the protocol hook when needed, drops po->bind_lock, and later restores po->num and re-registers the hook from the saved was_running value. That unlocked window can race with NETDEV_UNREGISTER. The notifier can observe the socket as not running, skip __unregister_prot_hook(), and invalidate the per-socket binding by setting po->ifindex to -1 and clearing po->prot_hook.dev. A one-member fanout group can still retain its shared fanout hook device pointer. When packet_set_ring() resumes, re-registering solely from the stale was_running state can re-add the fanout hook after the device has been unregistered. Treat po->ifindex == -1 as an invalidated binding after reacquiring po->bind_lock. This is distinct from ifindex 0, the normal unbound/wildcard state: ifindex -1 marks an existing device binding that was invalidated when the device was unregistered. Restore po->num as before, but do not re-register the hook if device unregister already detached the socket. Fixes: dc99f600698d ("packet: Add fanout support.") Link: https://lore.kernel.org/netdev/20260701113947.23180-1-david.lee@trailofbits.com/ Signed-off-by: David Lee Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260707104440.833129-1-david.lee@trailofbits.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()

2026-04-27T13:23:35+00:00

commit 2c054e17d9d41f1020376806c7f750834ced4dc5 upstream. In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points directly into the mmap'd TX ring buffer shared with userspace. The kernel validates the header via __packet_snd_vnet_parse() but then re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent userspace thread can modify the vnet_hdr fields between validation and use, bypassing all safety checks. The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr to a stack-local variable. All other vnet_hdr consumers in the kernel (tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX path is the only caller of virtio_net_hdr_to_skb() that reads directly from user-controlled shared memory. Fix this by copying vnet_hdr from the mmap'd ring buffer to a stack-local variable before validation and use, consistent with the approach used in packet_snd() and all other callers. Fixes: 1d036d25e560 ("packet: tpacket_snd gso and checksum offload") Signed-off-by: Bingquan Chen Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260418112006.78823-1-patzilla007@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

net: fix fanout UAF in packet_release() via NETDEV_UP race

2026-04-02T11:07:18+00:00

[ Upstream commit 42156f93d123436f2a27c468f18c966b7e5db796 ] `packet_release()` has a race window where `NETDEV_UP` can re-register a socket into a fanout group's `arr[]` array. The re-registration is not cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout array. `packet_release()` does NOT zero `po->num` in its `bind_lock` section. After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex` still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)` that already found the socket in `sklist` can re-register the hook. For fanout sockets, this re-registration calls `__fanout_link(sk, po)` which adds the socket back into `f->arr[]` and increments `f->num_members`, but does NOT increment `f->sk_ref`. The fix sets `po->num` to zero in `packet_release` while `bind_lock` is held to prevent NETDEV_UP from linking, preventing the race window. This bug was found following an additional audit with Claude Code based on CVE-2025-38617. Fixes: ce06b03e60fc ("packet: Add helpers to register/unregister ->prot_hook") Link: https://blog.calif.io/p/a-race-within-a-race-exploiting-cve Signed-off-by: Yochai Eisenrich Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260319200610.25101-1-echelonh@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net/packet: fix a race in packet_set_ring() and packet_notifier()

2025-08-15T10:09:05+00:00

commit 01d3c8417b9c1b884a8a981a3b886da556512f36 upstream. When packet_set_ring() releases po->bind_lock, another thread can run packet_notifier() and process an NETDEV_UP event. This race and the fix are both similar to that of commit 15fe076edea7 ("net/packet: fix a race in packet_bind() and packet_notifier()"). There too the packet_notifier NETDEV_UP event managed to run while a po->bind_lock critical section had to be temporarily released. And the fix was similarly to temporarily set po->num to zero to keep the socket unhooked until the lock is retaken. The po->bind_lock in packet_set_ring and packet_notifier precede the introduction of git history. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Quang Le Signed-off-by: Willem de Bruijn Link: https://patch.msgid.link/20250801175423.2970334-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

af_packet: fix soft lockup issue caused by tpacket_snd()

2025-07-24T06:53:13+00:00

commit 55f0bfc0370539213202f4ce1a07615327ac4713 upstream. When MSG_DONTWAIT is not set, the tpacket_snd operation will wait for pending_refcnt to decrement to zero before returning. The pending_refcnt is decremented by 1 when the skb->destructor function is called, indicating that the skb has been successfully sent and needs to be destroyed. If an error occurs during this process, the tpacket_snd() function will exit and return error, but pending_refcnt may not yet have decremented to zero. Assuming the next send operation is executed immediately, but there are no available frames to be sent in tx_ring (i.e., packet_current_frame returns NULL), and skb is also NULL, the function will not execute wait_for_completion_interruptible_timeout() to yield the CPU. Instead, it will enter a do-while loop, waiting for pending_refcnt to be zero. Even if the previous skb has completed transmission, the skb->destructor function can only be invoked in the ksoftirqd thread (assuming NAPI threading is enabled). When both the ksoftirqd thread and the tpacket_snd operation happen to run on the same CPU, and the CPU trapped in the do-while loop without yielding, the ksoftirqd thread will not get scheduled to run. As a result, pending_refcnt will never be reduced to zero, and the do-while loop cannot exit, eventually leading to a CPU soft lockup issue. In fact, skb is true for all but the first iterations of that loop, and as long as pending_refcnt is not zero, even if incremented by a previous call, wait_for_completion_interruptible_timeout() should be executed to yield the CPU, allowing the ksoftirqd thread to be scheduled. Therefore, the execution condition of this function should be modified to check if pending_refcnt is not zero, instead of check skb. - if (need_wait && skb) { + if (need_wait && packet_read_pending(&po->tx_ring)) { As a result, the judgment conditions are duplicated with the end code of the while loop, and packet_read_pending() is a very expensive function. Actually, this loop can only exit when ph is NULL, so the loop condition can be changed to while (1), and in the "ph = NULL" branch, if the subsequent condition of if is not met, the loop can break directly. Now, the loop logic remains the same as origin but is clearer and more obvious. Fixes: 89ed5b519004 ("af_packet: Block execution of tasks waiting for transmit to complete in AF_PACKET") Cc: stable@kernel.org Suggested-by: LongJun Tang Signed-off-by: Yun Lu Reviewed-by: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

af_packet: fix the SO_SNDTIMEO constraint not effective on tpacked_snd()

2025-07-24T06:53:13+00:00

commit c1ba3c0cbdb5e53a8ec5d708e99cd4c497028a13 upstream. Due to the changes in commit 581073f626e3 ("af_packet: do not call packet_read_pending() from tpacket_destruct_skb()"), every time tpacket_destruct_skb() is executed, the skb_completion is marked as completed. When wait_for_completion_interruptible_timeout() returns completed, the pending_refcnt has not yet been reduced to zero. Therefore, when ph is NULL, the wait function may need to be called multiple times until packet_read_pending() finally returns zero. We should call sock_sndtimeo() only once, otherwise the SO_SNDTIMEO constraint could be way off. Fixes: 581073f626e3 ("af_packet: do not call packet_read_pending() from tpacket_destruct_skb()") Cc: stable@kernel.org Suggested-by: Eric Dumazet Signed-off-by: Yun Lu Reviewed-by: Eric Dumazet Reviewed-by: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman