CVE-2026-64188

Summary

In the Linux kernel, the following vulnerability has been resolved:

net: qualcomm: rmnet: fix endpoint use-after-free in rmnet_dellink()

rmnet_dellink() removes the endpoint from the hash table with hlist_del_init_rcu() and then immediately frees it with kfree(). However, RCU readers on the receive path (rmnet_rx_handler -> __rmnet_map_ingress_handler) may still hold a reference to the endpoint and dereference ep->egress_dev after the memory has been freed. The endpoint is a kmalloc-32 object, and the stale read at offset 8 corresponds to the egress_dev pointer.

BUG: unable to handle page fault for address: ffffffffde942eef Oops: 0002 [#1] SMP NOPTI CPU: 1 UID: 0 PID: 137 Comm: poc_write Not tainted 7.0.0+ #4 PREEMPTLAZY RIP: 0010:rmnet_vnd_rx_fixup (rmnet_vnd.c:27) Call Trace: <TASK> __rmnet_map_ingress_handler (rmnet_handlers.c:48 rmnet_handlers.c:101) rmnet_rx_handler (rmnet_handlers.c:129 rmnet_handlers.c:235) __netif_receive_skb_core.constprop.0 (net/core/dev.c:6096) __netif_receive_skb_one_core (net/core/dev.c:6208) netif_receive_skb (net/core/dev.c:6467) tun_get_user (drivers/net/tun.c:1955) tun_chr_write_iter (drivers/net/tun.c:2003) vfs_write (fs/read_write.c:688) ksys_write (fs/read_write.c:740) </TASK>

Add an rcu_head field to struct rmnet_endpoint and replace kfree() with kfree_rcu() so the endpoint memory remains valid through the RCU grace period. Also remove the rmnet_vnd_dellink() call and inline only the nr_rmnet_devs decrement, since rmnet_vnd_dellink() would set ep->egress_dev to NULL during the grace period, creating a data race with lockless readers.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/c4e676c3505c5058922dc1a6f1ded795f6758135
• https://git.kernel.org/stable/c/9918698cf3aee4032e12bb42fd5a951dc465339b
• https://git.kernel.org/stable/c/310b93246bfec7d4452507e0c15477377ed9f025
• https://git.kernel.org/stable/c/1078ae8175777e80c9637996fb4a46c55f0ce576
• https://git.kernel.org/stable/c/41e06fcc5df0774d212e70c5b503fc769492bce3
• https://git.kernel.org/stable/c/8b17adf6d4fb6bf61fa4c3f58366a7c082799a71
• https://git.kernel.org/stable/c/f193e38cb257d033060b63f1cfd94af076b3a2ab
• https://git.kernel.org/stable/c/d00c953a8f69921f484b629801766da68f27f658

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