CVE-2026-89780net: qualcomm: rmnet: restore skb->dev on deaggregated frames

Official description

In the Linux kernel, the following vulnerability has been resolved: net: qualcomm: rmnet: restore skb->dev on deaggregated frames rmnet_map_deaggregate() allocates each sub-frame with alloc_skb() and leaves skb->dev NULL. __rmnet_map_ingress_handler() assigns skb->dev = ep->egress_dev only on the data path, but a MAP command frame is dispatched to rmnet_map_command() before that, so rmnet_map_send_ack() runs netif_tx_lock(skb->dev) on a NULL device. An unprivileged user reaches this by unsharing a user+net namespace, creating an rmnet link over a tap device with INGRESS_DEAGGREGATION and INGRESS_MAP_COMMANDS, and writing an aggregated frame carrying a flow-control command to the tap fd. Restore the assignment dropped by 378e25357ac7, so every skb leaving rmnet_map_deaggregate() has a valid device. BUG: KASAN: null-ptr-deref in _raw_spin_lock (kernel/locking/spinlock.c:158) Write of size 4 at addr 00000000000004b4 by task exploit/144 Call Trace: _raw_spin_lock (kernel/locking/spinlock.c:158) netif_tx_lock (net/sched/sch_generic.c:497) rmnet_map_command (drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c:67) rmnet_rx_handler (drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c:125) __netif_receive_skb_core.constprop.0 (net/core/dev.c:6103) ... __netif_receive_skb_one_core (net/core/dev.c:6214) netif_receive_skb (net/core/dev.c:6474) tun_get_user (drivers/net/tun.c:1966) tun_chr_write_iter (drivers/net/tun.c:2012) vfs_write (fs/read_write.c:687) ksys_write (fs/read_write.c:739) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Kernel panic - not syncing: Fatal exception in interrupt

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/5aaa7409c1b4ca4c60d66e2afa99703bf4eb7ddd
• https://git.kernel.org/stable/c/9b78ab84ddf97c06a8567edb62b6c0fd582f9a62
• https://git.kernel.org/stable/c/9d18c6c6cd1666b2cb7915cad052e22abf520997
• https://git.kernel.org/stable/c/4bcef54e4a3355a62d9ad90729fe563435ec76c3
• https://git.kernel.org/stable/c/b14c22c31d9e30f38ea1693ac06d318f32258f5d
• https://git.kernel.org/stable/c/7abe769e72c792e5f9eb273813eb3ecd8389854c
• https://git.kernel.org/stable/c/200460a0793dc6af97d3b36d92ac245350ac26fc
• https://git.kernel.org/stable/c/a66734a1c5e36525ea07e9f4547fddc51e916de3