CVE-2026-64188: net: qualcomm: rmnet: fix endpoint use-after-free in rmnet_dellink()

From: Greg Kroah-Hartman <[email protected]>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2026-64188 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 5.10.260 with commit c4e676c3505c5058922dc1a6f1ded795f6758135
	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 5.15.211 with commit 9918698cf3aee4032e12bb42fd5a951dc465339b
	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 6.1.177 with commit 310b93246bfec7d4452507e0c15477377ed9f025
	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 6.6.144 with commit 1078ae8175777e80c9637996fb4a46c55f0ce576
	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 6.12.95 with commit 41e06fcc5df0774d212e70c5b503fc769492bce3
	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 6.18.37 with commit 8b17adf6d4fb6bf61fa4c3f58366a7c082799a71
	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 7.0.14 with commit f193e38cb257d033060b63f1cfd94af076b3a2ab
	Issue introduced in 4.14 with commit ceed73a2cf4aff2921802aa3d21d45280677547d and fixed in 7.1 with commit d00c953a8f69921f484b629801766da68f27f658

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-64188
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
	drivers/net/ethernet/qualcomm/rmnet/rmnet_config.h


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	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